Abstract: Aspects of the subject disclosure may include a power splitter. The power splitter can include a first splitter branch having a first amplifier with passive components, a second splitter branch having a second amplifier with passive components. The first splitter branch is substantially electrically isolated from the second splitter branch by configuring the first and second splitter branches to have similar phase delays. Outputs of the power splitter can be electrically coupled to the multi-stage amplifier. The power splitter can be manufactured on a single semiconductor die or integrally formed on the same semiconductor die with other circuits such as the multi-stage amplifier. Other embodiments are disclosed.

Abstract: A transmission driver includes a pulse generator and a current mode logic driver. The pulse generator is configured to generate and output a first pulse signal by synchronizing at a falling edge time point of a first input signal, and generate and output a second pulse signal by synchronizing at a falling edge time point of a second input signal. The current mode logic driver is configured to output a pre-emphasis signal to which pre-emphasis technique has been applied by changing a first load resistance value and a second load resistance value based on the first pulse signal and the second pulse signal, respectively.

Abstract: Provided is a power amplification circuit that includes: a first transistor that has an emitter to which a first radio frequency signal is supplied, a base to which a first DC control current or DC control voltage is supplied and a collector that outputs a first output signal that corresponds to the first radio frequency signal; a first amplifier that amplifies the first output signal and outputs a first amplified signal; and a first control circuit that supplies the first DC control current or DC control voltage to the base of the first transistor in order to control output of the first output signal.

Abstract: An operational amplifier applicable to a display device is provided. The operational amplifier having multiple output stages. The operational amplifier includes an input stage, an output stage selection module and a plurality of output stages. The output stage selection module is coupled to the input stage. Each of the output stages is coupled to the output stage selection module and is coupleable to drive a corresponding one of a plurality of loads. The output stage selection module is configured to selectively couple or discouple each of the output stages respectively to the input stage according to a plurality of selection signal. Furthermore, a load driving apparatus and a grayscale voltage generating circuit are also provided.

Abstract: An amplifier system has an amplifier for amplifying a plurality of input signals from a plurality of different channels, and a plurality of demodulators each operatively coupled with the amplifier for receiving amplified input signals from the amplifier. Each demodulator is configured to demodulate a single amplified input channel signal from a single channel of the plurality of different channels. The system thus also has a plurality of filters, coupled with each of the demodulators, for mitigating the noise.

Abstract: A Lange coupler having a first plurality of lines on a first level and a second plurality of lines on a second level. At least one line on the first level is cross-coupled to a respective line on the second level via electromagnetic waves traveling through the first and second plurality of lines. The first and second plurality of lines may be made of metal, and the first level may be higher than the second level. A substrate may be provided into which the first and second plurality of lines are etched so as to define an on-chip Lange coupler.

Abstract: The invention relates to a receiver for a near-field chip-to-chip multichannel transmission system such as the capacitive or inductive links used for vertical signal transmission between the stacked chips of a system-in-package. A receiver for near-field chip-to-chip multichannel transmission providing 4 transmission channels for digital transmission between two monolithic integrated circuits comprises 4 coupling devices (211) (212) (213) (214), each of said coupling devices being a planar winding sensitive to magnetic field variations. A multiple-input-port and multiple-output-port amplifier (23) has 4 input ports, each of said input ports being connected to one and only one of said coupling devices (211) (212) (213) (214).

Abstract: An output matching network comprising a plurality of impedance matching circuits. The inputs of each of the plurality of impedance matching circuits are connected to a first input of the output matching network. The outputs of each of the plurality of impedance matching circuits are connected to a plurality of first outputs of the output matching network. One of the plurality of impedance matching circuits is active at a given time. The active impedance matching circuit of the plurality of impedance matching circuits exhibits a first input impendence at a first frequency band. Each inactive impedance matching circuit of the plurality of impedance matching circuits exhibits a second input impedance at the first frequency band. The second input impendence is at least 10 times greater than the first input impendence.

Abstract: Existing multi-band/multi-mode (MB/MM) power amplifiers (PAs) use separate signal paths for the different covered frequency bands. This results in a large degree of hardware duplication and to a large die size and cost. Solutions that achieve hardware sharing between the different signal paths of MB/MM PAs are shown. Such sharing includes bias circuit and bypass capacitors sharing, as well as sharing front-end stages and the output stage of the PA. Signal multiplexing may be realized in the transmitter or at the PA front-end while the signal de-multiplexing can be realized either in the PA output stage or at the front-end of the output stage. Such circuits can be applied with saturated and linear MB/MM PAs with adjacent or non-adjacent bands.

Abstract: An apparatus comprising an amplifier and a switch network. The amplifier may be configured to generate a plurality of output signals in response to an input signal. The switch network may be configured to provide (i) a first path when a power signal is not present and (ii) a second path when said power signal is present. The first path may activate a first of the plurality of output signals. The second path may activate all of the plurality of output signals. An impedance may be connected to the amplifier only when the first path is activated.

Abstract: An apparatus comprising an amplifier and a switch network. The amplifier may be configured to generate a plurality of output signals in response to an input signal. The switch network may be configured to provide (i) a first path when a power signal is not present and (ii) a second path when said power signal is present. The first path may activate a first of the plurality of output signals. The second path may activate all of the plurality of output signals. An impedance may be connected to the amplifier only when the first path is activated.

Abstract: Power amplifiers (PAs) using a Doherty or other power output level sensitive configuration have been employed for several years in telecommunications (as well as other applications) to take advantage of efficiency gains. For many of these applications, baseband signals are predistorted to compensate for nonlinearities in the PAs, but because there is a “switching event” in a Doherty-type amplifier (for example), the nonlinearities become dynamically varying. As a result, digital predistortion (DPD) becomes increasingly difficult to perform. Here, DPD modules are provided that adapt to changes in dynamically varying PAs based on a determination of the average power or other relevant metric prior to transmission.

Abstract: A modulation device includes a signal input for receiving a data stream to be modulated and a first and a second signal output. At least one first complex component is derived from the data stream in a coding device. A first and a second high-frequency signal are output via the signal outputs. The first and second high-frequency signals are derived from the at least one first complex component and are distinguished by the fact that the second high-frequency signal has a phase shift of substantially 90° with respect to the first high-frequency signal.

Abstract: A wireless communication device includes an RF transceiver configured to up convert a base band signal to a transmitting RF signal, a configurable matrix power amplifier circuit configured to amplify the transmitting RF signal to produce an amplified RF signal, and an antenna configured to transmit a wireless signal in response to the amplified RF signal.

Abstract: An audio amplifier (3) for a mobile telephone (1) is disclosed. The audio amplifier (3) comprises first and second output stages (11, 12), each for coupling to a respective one of first and second loudspeakers (4, 5), and switching circuitry (10) adapted to respond to a switching signal by switching an output signal from a common input stage (7, 8, 9) to the first output stage (11) when the switching signal is in a first state and to the second output stage (12) when the switching signal is in a second state.

Abstract: A semiconductor device and a radio frequency circuit which are appropriate for multiband, multimode performance can be realized as a semiconductor device including a field-effect transistor formed on a semiconductor substrate, and include: ohmic electrodes serving as source and drain electrodes of the field-effect transistor, first and second Schottky electrodes provided between the ohmic electrodes and serving as gate electrodes of the field-effect transistor, and a third Schottky electrode provided and grounded between the first and second Schottky electrodes.

Abstract: The invention relates to an amplifier capable of producing a plurality of output signals, these output signals being controlled by a plurality of input signals. A multiple-input and multiple-output amplifier of the invention includes 4 signal input terminals, 4 signal output terminals, 4 active sub-circuits and a feedback network. Each active sub-circuit has a sub-circuit input terminals connected to one of the signal input terminals, a sub-circuit output terminal connected to one of the signal output terminals and a sub-circuit common terminal. The feedback network uses mutual induction between windings. The feedback network has terminals connected to the sub-circuit common terminal of the active sub-circuits. The feedback network presents an impedance matrix producing a negative feedback such that the transfer admittance matrix of the multiple-input and multiple-output amplifier approximates a given admittance matrix.

Abstract: The invention relates to an amplifier capable of producing a plurality of currents at its output terminals, these currents being controlled by a plurality of input voltages. A multiple-input and multiple-output amplifier of the invention includes 4 signal input terminals, 4 signal output terminals, 4 active sub-circuits and a feedback network. Each active sub-circuit has a sub-circuit input terminal connected to one of the signal input terminals, a sub-circuit output terminal connected to one of the signal output terminals and a sub-circuit common terminal. The feedback network has terminals connected to the sub-circuit common terminal of each active sub-circuit. The feedback network presents, in a known frequency band, an impedance matrix producing a negative feedback such that the transfer admittance matrix of the multiple-input and multiple-output amplifier approximates a given admittance matrix.

Abstract: An operational amplifier circuit includes: an input differential stage circuit supplied with power supply voltages in a first voltage range; and an output stage circuit supplied with power supply voltages in a second voltage range which is different from the first voltage range. The operational amplifier circuit amplifies a signal supplied to the input differential stage circuit and outputs the amplified signal from the output stage circuit to drive a load.

Abstract: A non-inverting amplifier includes n external input terminals which receive n (n?3) input voltage signals having a constant sum of voltages, respectively, n amplification units each including n?1 internal input terminals connected to n?1 terminals of the n external input terminals in a different combination for each of the amplification units, n?1 voltage-to-current converters which convert input voltage signals from the internal input terminals into current signals, and a load which converts an added current signal obtained by adding up the current signals into an output voltage signal, and n external output terminals which output n output voltage signals from the n amplification units.

Abstract: The grayscale voltage generating circuit comprises an input/driving stage circuit amplifying an input voltage and output stage circuits receiving a output voltage from the input/driving stage circuit, outputting one of the grayscale voltages, and having a capacitor to keep a voltage level of the grayscale voltage. The output stage circuits are sequentially switched to be connected with the input/driving stage circuit, and an output voltage from the input/driving stage circuit is fed to the plurality of output stage circuits in order. Each of the output stage circuits outputs the grayscale voltage based on a voltage held in the capacitor irrespective of connection with the input/driving stage circuit.

Abstract: A multi-fferential amplifier system includes an amplifier having a plurality of amplifier inputs and a plurality of amplifier outputs; a plurality of input terminals for receiving a plurality of inputs and being interconnected with the amplifier inputs through a plurality of input impedances, respectively, and a feedback network including a plurality of summing circuits for combining the plurality of amplifier outputs in a plurality of different sets of groups each group numbering one fewer than the plurality, respectively, and feeding back the sum of each group of amplifier outputs to the remaining amplifier input for maintaining the difference between any group of amplifier outputs proportional to the difference of a corresponding group of inputs at the terminals and maintaining the average value of the amplifier outputs constant and unrelated to the inputs at the terminal.

Abstract: A wideband splitter includes a core amplifier for receiving a single pair of differential input signals and providing first and second pairs of differential output signals. The first pair of differential output signals and the second pair of differential outputs have substantially identical characteristics. A signal gain is implemented between the received single pair of differential input signals and the first and second pair of differential output signals. The signal gain is substantially constant across the frequency bandwidth of the core amplifier. A bandwidth peaking network is coupled to the core amplifier and includes (a) a first coil and a first resistor connected in series and (b) a second coil and a second resistor connected in series. The bandwidth peaking network is configured to increase the frequency bandwidth of the core amplifier.

Abstract: A radio frequency (RF) front-end includes a plurality of power amplifier modules and a plurality of impedance matching circuits. Each of the plurality of impedance matching circuits includes an input connection and an output connection, wherein outputs of the plurality of power amplifier modules are coupled to corresponding input connections of the plurality of impedance matching circuits to provide a desired loading of the plurality of power amplifier modules and wherein the output connections of the plurality of impedance matching circuits are coupled together to add power of the plurality of power amplifiers.

Abstract: A power amplification apparatus includes, between a first amplification element for amplifying an input signal and a first output terminal, a second amplification element for further amplifying the input signal amplified in the first amplification element to output to the first output terminal, and a first switch element for controlling the second amplification element to be stop condition. Further, between the first amplification element and a second output terminal, a second switch circuit for controlling the supply of an output from the first amplification element to the second output terminal is provided. When outputting a medium power, the operation efficiency of the power amplification apparatus is improved by reducing a power consumption. Thereby, a total operation efficiency of the power amplification apparatus which outputs either the input signal amplified to a large power or the input signal amplified to a medium power by switching is improved.

Abstract: An amplifier circuit (1) is disclosed, wherein with a view to reducing the leakage power of the amplifier circuit (1) a current path (6) is provided between a first output terminal (A1) and a second output terminal (A2) of the amplifier circuit, said current path being open in the case of an uptake of energy at the output of the amplifier circuit (1), so that the electrical energy taken up by the one output terminal (A1) can be drained away immediately via the other output terminal (A2). If no uptake of energy is taking place via the output of the amplifier circuit (1) but instead electrical energy is being released by the amplifier circuit (1), the current path (6) between the two output terminals (A1, A2) is closed.

Abstract: A variable impedance load (104) is provided at the output of a radio frequency (RF) driver amplifier (102) having a variable gain. In an exemplary embodiment, the variable load (104) comprises a resistor (R) in series with a semiconductor device (M1). The semiconductor device (M1) has an impedance level determined by a drive current. The value of the drive current is related to the gain of the RF driver amplifier (102).

Abstract: An apparatus comprising a first circuit and a second circuit. The first circuit may be configured to generate an intermediate signal in response to an input signal. The second circuit may be configured to generate a plurality of output signals in response to the intermediate signal. Each of the output signals may be (i) an amplified versions of the input signal and (ii) isolated between each of the other output signals.

Abstract: A high-frequency amplifier that can reduce the size, weight and price of a device that contains this high-frequency amplifier. The high-frequency amplifier has, for example, an input matching circuit of the low-pass type and an input matching circuit of the high-pass type, connected in parallel and provided at the input side or terminal of a power amplification circuit. Matching is thereby performed corresponding to either one of two kinds of transmission input signals, whose frequencies are different from each other, by the input matching circuit of the low-pass type, and by the input matching circuit of the high-pass type, respectively. Moreover, for example, an output matching circuit of the low-pass type and an output matching circuit of the high-pass type are connected in parallel and provided at the output side or terminal of the power amplification circuit.

Abstract: An amplifier, suitable for radio frequency applications, has good noise properties because of a special transistor configuration. A pair of transistors is connected in a cascode configuration, to overcome the Miller effect. The transistors have their bases driven by a common current source. The main current paths from ground to each of the output terminals are essentially noise-free. One of the transistors, acting as a transconductance amplifier, does introduce some noise though this is minimized by the use of an inductor. A third transistor forms a current source for the current path to one of the output terminals. A differential output is achieved at the output terminals because the pair of transistors has complementary outputs. In another embodiment, a capacitor is connected across the collector and base electrodes of one of the transistors to introduce a further stage of gain.

Abstract: An active quadrature power splitter having low power consumption is small in size and is inexpensive, for obtaining two output signals of which the phase difference is 90 degrees. Since the active quadrature power splitter operates as a microwave amplifier for obtaining two amplified microwave outputs having an equal magnitude and a phase difference of 90 degrees by using a matching circuit of the amplifier, a power gain can be obtained. Also, since a single FET or HBT is used and two output signals are generated in an output impedance matching circuit, the circuit becomes simplified. Therefore, the circuit can be easily implemented in a monolithic microwave IC and the chip size can be reduced.

Abstract: First and second amplifiers are coupled together to provide complementary output signals at respective output terminals in response to application of operating potentials to first and second supply terminals of each amplifier and application of an input signal to at least the first amplifier. A switching circuit, responsive to a first level of a tri-state control signal supplied thereto, applies the operating potentials individually to the first and second supply terminals of each amplifier and concurrently couples the input signal to the input of the first amplifier and, responsive to a second level of the tri-state control signal, isolates all of the amplifier supply terminals and decouples the input signal. Transient disturbances are minimized by AC coupling the input signal and applying a common mode signal from a common mode source to the AC coupling, to a reference input of each amplifier and to the output terminal of each amplifier.

Abstract: The circuit employs two bipolar transistors, five resistors and a capacitor and can be primarily utilized as a broadband pre-amplifier and also as an oscillator or a mixer. A first transistor is connected to the circuit input and ground. A second transistor is connected to the collector of the first transistor and the supply voltage. One circuit output is connected to the second transistor. Another circuit output is connected to the first transistor via a resistor. The emitter of the first transistor is connected to the second transistor via a second resistor. A third resistor is connected between the base and collector of the first transistor. A fourth resistor is connected between the base and collector of the second transistor.

Abstract: An electronic driver circuit for low-impedance loads, being of a type which comprises an input terminal (IN) to which a voltage signal (Vin) is applied for alternate transfer to an output, and a plurality of output terminals (OUTi), each connected to a corresponding electric load (2), further comprises, between the input terminal and the output terminals, a single operational amplifier (3) having multiple output stages (7), one for each output terminal (OUTi). The operational amplifier (3) is of the single-ended or fully differential multistage type and allows each load to be driven alternately by activation of the corresponding output stage (7i).

Abstract: An oscilloscope preamplifier includes N inputs and Z outputs. A programmable cross-point multiplexer provides a first operating mode in which each of N inputs is connected to a different output thereby providing a preamplifier with Z channels, a second operating mode in which one input is multiplexed to all the outputs which are interleaved to maximize the sampling rate, and a range of operating modes in between. The programmable multiplexer includes a switching amplifier connected between each input and each output. Dials on the preamp select the mode by causing a microprocessor to program latches which activate or deactivate the switching amplifiers. A voltage divider is connected across inputs of the multiplexer to provide a programmable attenuator with selectable attenuation levels.

Abstract: An audio amplification circuit includes a ganged pair of logarithmic potentiometers, each potentiometer of the pair having an input terminal, an output terminal, and a wiper terminal. The input terminals of each potentiometer are adapted for connection to an audio input signal from an audio device such as a microphone. A preamplifier stage having an input is connected to the wiper terminals of both logarithmic potentiometers. An amplification stage has a matched pair of operational amplifiers with each operational amplifier having an input connected to the output of the preamplifier stage. Each operational amplifier has a feedback loop which includes the resistance of at least one of the logarithmic potentiometers between the output terminal and the wiper terminal of said logarithmic potentiometer. The outputs of the matched pair of operational amplifiers constitute the outputs of the amplification stage. The outputs may be daisy-chained together, and a floating output stage is also provided.

Abstract: A multi-output power amplifier is disclosed. The amplifier is divided into two stages. A single voltage amplifier is used as an input amplifying stage and several current amplifiers are used as a second amplifying stage. The inputs to the current amplifiers share a common connection to the output of the voltage amplifier and feedback is provided from the current amplifier outputs to the voltage amplifier input.

Abstract: An active load applied to the gate transmission line termination of distributed power devices reduces the low frequency noise power appearing at the output of the device. The active load, including at least one active device such as a field effect transistor, operates by transforming the input impedance of a low noise amplifier to the desired load impedance. The active load is connected to one end of an input transmission line having a plurality of impedances connected in electrical series. An input terminal is connected to the opposite end. An output transmission line, also having a plurality of impedances connected in series, has an output terminal at one end and a terminating output impedance at the other. A plurality of active devices are connected to junction points between the series connected impedances of the input and output lines.

Abstract: A charge transfer circuit includes an input terminal for receiving an input electrical charge, a transconductance amplifier having first and second inputs including an inverting input, and first and second differential current outputs, and a multiple output stage circuit responsive to the differential current outputs for producing two or more electrical current output signals whose values are related to the values of the differential current outputs and to each other. Also included is a feedback loop for delivering one of the electrical current output signals to the inverting input of the transconductance amplifier, and an integrator for integrating another of the electrical current output signals to produce an output electrical charge whose value is related to the value of the input electrical charge.

Abstract: Apparatus and methods are disclosed for providing a low power, low noise preamplifier, especially useful with a Forward Looking Infrared (FLIR) sensor array. Utilizing a differential amplifier, where one half of the differential pair is shared among a plurality of channels, the power consumption of the amplifier is effectively reduced. Such an arrangement also eliminates the need for bulky coupling capacitors used in ac-coupled, single ended amplifiers. In addition, cross-talk between sensor outputs caused by detector ground impedance is reduced.

Abstract: A radio frequency variable gain amplifier (204) has a plurality of outputs. The amplifier (204) includes a transistor amplifier (330) having a plurality of switchable fixed gain states for amplifying an oscillator signal. The amplifier (204) includes a biasing circuit (302, 306, 312, and 316) for selectively biasing the transistor amplifier (330) to produce the plurality of switchable fixed gain states. The biasing circuit (302, 306, 312, and 316) includes switches (310 and 320) for switching between the switchable fixed gain states of the transistor amplifier (330).

Abstract: A radio frequency amplifier comprises a differential amplifier having a pair of differential first and second transistors and a first and a second load resistor; an emitter grounded amplifier having a third transistor and a third load resistor; and a reference voltage generator having a constant-current source formed by a fourth transistor and a fourth load resistor. The emitter grounded amplifier receives a high frequency input signal and outputs a single signal output. One input node of the differential amplifier receives the output from the emitter grounded amplifier and the other input node receives a reference voltage from the reference voltage generator. The third and fourth transistors form a current-mirror circuit.

Abstract: A two dimensional distributed amplifier phase shifter having a distributed reference amplifier circuit generating a reference signal, the reference amplifier circuit having its input connected to one end of a plurality of serially connected microstrip transmission lines. The phase shifter further has a plurality of phase shifted amplifier circuits, one associated with each of the microstrip transmission lines. Each phase shifted amplifier circuit has an input connected to an end of its associated microstrip transmission line which is opposite the reference amplifier circuit and generates an output signal, phase shifted from the reference signal or the output signal of an adjacent phase shifted amplifier by a predetermined phase angle. The phase shifter may be fabricated as a monolithic microwave integrated circuit.

Abstract: The present invention concerns a high impedance signal source driving a relatively low input impedance mechanical resonating device such as a ceramic filter having an input impedance which varies with frequency. The high impedance source is further loaded by a resonant circuit tuned to the center frequency of the mechanical resonating device. The skirts of the resonant tuned circuit decrease in impedance on both sides of the center frequency of interest substantially compensating for the change of circuit gain with frequency due to the change of input impedance with frequency of the ceramic filter.

Abstract: A foreground music sound system includes at least one complementary array of speakers (12) comprising a bass frequency speaker (20) and a plurality of microspeackers (14-18). The complementary speaker array may be designed to provide full frequency response with substantially uniform sound coverage for a wide variety of acoustic environments. A current amplifier (25) is responsive to a music signal input and a microphone signal input to directly drive the speakers. The amplifier (25) is a high current, low impedance amplifier so that it is capable of driving a large number of speakers, without the need for matching transformers at each speaker.

Abstract: A power splitter (10), including a feedback amplifier (16) and matching network (18), is disclosed for splitting the output of a signal source (12) to be applied to a processing system (14). The feedback amplifier includes a gain stage (20) and active load (22). The gain stage includes a field-effect transistor (FET) (Q1) and feedback components (LF and RF) that provide the amplification required to give the power splitter unity gain. An inductive element (LD) gives the amplifier the desired bandwidth and a dual-gate FET (Q2) is employed as the active load to reduce loading of the gain stage. The matching network includes a plurality of stages (e.g., 24), each of which includes a source follower FET (e.g., Q3 ) and a single-gate active load FET (e.g., Q4). The resultant power splitter provides the desired equal power, matched phase outputs with suitable isolation and minimal insertion losses.

Abstract: An all-differential operational amplifier (20) has a first input (22) and a second input (24) and correspondingly has a first output (26) and a second output (28), fed back on its own input respectively through a first (34) and second (36) impedance which are generally resistive and have identical values. The first output is connected to the second input of the operational amplifier across a third impedance (32). A fourth impedance (30), equal in value to the third impedance, is connected in series to the first input and acts as input terminal of the converter. The resistive components of the impedance can be implemented as switched capacitors.

Abstract: A dual path amplifier circuit configuration to obtain wideband and precision DC response includes a wideband voltage amplifier, an input termination, a virtual ground feedback amplifier, and a compensated attenuator. The circuit allows precision DC and wideband measurements through a common signal probe while maintaining the input impedance of the measurement instrument. An additional feature of the circuit is to selectively allow DC measurements before or after an attenuator. The circuit can provide combined wideband and DC signal output or separate wideband and DC outputs. Additionally, the circuit can use a DC offset to null the DC level of an input signal.

Abstract: A feedback amplifier for providing an amplified signal to first and second utilization networks includes first and second feedback paths. The amplifier output is coupled via a first coupling resistor to a first terminal to which the first utilization network is connected, and via a second coupling resistor to a second terminal to which the second utilization network is subject to being connected. The first feedback path couples the amplifier output to the amplifier input exclusive of the first coupling resistor. The second feedback path couples the amplifier output to the amplifier input and includes the second coupling resistor. The amplifier output signal remains substantially constant in the presence or absence of said second utilization network.

Abstract: A bank of differential amplifier circuits includes specialized circuits to provide multi-channel differencing with a minimum number of active devices such that the differences between pairs of analog input signals, such as available from patient monitoring electrodes, are derived with half the number of active devices normally utilized. In one embodiment, two operational amplifier circuits are used in a differencing channel which functions together to provide differencing, a properly delayed input signal for use in another differencing channel, high input impedance buffering, a low impedance output for each differential amplifier channel, time-coincident, matched outputs for each differential amplifier channel, and with an additional operational amplifier, a DC rejection circuit which does not affect the low output impedance or the differencing function, thereby to eliminate the necessity of providing separate buffers and active delay circuits which can result in the use of twice the number of active devices.