Abstract: An integrated-circuit analog-to-digital converter of the successive-approximation type formed on a single monolithic chip. The converter is made by a diffusion process wherein certain portions of the chip are formed with normal-mode linear transistors, and other portions are formed with inverted mode I.sup.2 L transistors. The normal-mode transistors provide a switchable current-source DAC, a set of three-state output buffers, and a comparator. The inverted mode transistors provide an internal clock and successive-approximation control circuitry for the DAC. The chip also includes a voltage reference to provide for absolute analog-to-digital conversions.

Abstract: An integrated circuit voltage regulator is of the kind having a pass transistor connected collector-to-emitter between the input V.sub.CC conductor and the regulated-voltage output conductor, a current source circuit supplying a base bias current to the pass transistor and a voltage reference and feedback regulator circuit connected between the output voltage conductor and the base of the pass transistor. A protective circuit against high voltage transients adding to V.sub.CC voltage comprises a transistor connected collector-to-emitter between the pass-transistor base and ground has a resistor paralleling the base-emitter junction, which resistor is resistively coupled to the input V.sub.CC line to shunt away the pass-transistor bias current whenever the V.sub.CC voltage level exceeds a value just under the latch-back breakdown voltage of the pass transistor. A zener diode directly connected across the DC input voltage conduction renders the regulator even more tolerant of high voltage transients.

Abstract: A voltage regulator having a series regulator operated by a shunt regulator.

Abstract: A bias generator for use in CML gate circuits provides an output reference voltage that is substantially independent of variations in supply voltage over a wide temperature range. The bias generator includes a temperature and voltage compensating circuit portion which is formed of an emitter resistor and a diode-connected transistor. The emitter resistor is used to control the output reference voltage for the lower temperatures and the base-emitter voltage of the transistor determines the output reference voltage for the higher temperatures.

Abstract: A circuit for generating a reference voltage with a predetermined temperature drift includes a supply circuit; output terminals; a series circuit connected to the supply circuit and between the output terminals including a network and a circuit for generating an electrical variable having a positive temperature coefficient; and a regulator for negative feedback of an operating point setting having an input circuit connected to the circuit for generating an electrical variable having a positive temperature coefficient and an output circuit connected to the output terminals.

Abstract: A series voltage regulator having a regulating transistor (T.sub.1) arranged with its emitter-to-collector path in a series arm of the regulator, the base of which is controlled via a control transistor (T.sub.2) by a first differential amplifier (V) which compares a reference voltage (U.sub.REF) with a voltage proportional to the voltage (U.sub.2) of the regulator output. A differential circuit (V.sub.2) which compares the collector-to-emitter voltage of the regulating transistor (T.sub.1) with an auxiliary voltage (U.sub.3) is provided, the output of which is followed by a current limiting circuit (T.sub.3) which acts upon control transistor (T.sub.2). The auxiliary voltage (U.sub.3) is larger than the collector-to-emitter voltage of the regulating transistor (T.sub.1) which occurs at the beginning of the saturation state of the regulating transistor. The current limiting circuit (T.sub.3) limits the current delivered by the control transistor (T.sub.2) to the base of the regulating transistor (T.sub.

Abstract: An output stage control circuit comprises an output driving means connected to a load for driving the same, a control means for taking out detection signals corresponding to signals flowing to the load and supplying analog control signals to the output driving means and a reference signal supply means for supplying reference signals to the control means, in which the analog control signals are generated depending on the detection signals and the reference signal, and the load is driven in an analogous manner by the output driving means depending on the analog control signals. The output stage control circuit can continuously supply the current to the load thereby operating the load stably with less occurrence of noises and stably for a long period of time.

Abstract: A semiconductor device having a circuit for regulating the external power supply voltage applied to the chip. When numerous chips are used in an electronic circuit having an external power supply voltage, variations in the electrical characteristics, such as the total power supply current, of each chip, become a problem. According to the present invention, variations in the electrical characteristics can be reduced by compensating the chip-to-chip fluctuations of the conductance of transistors (FETs) contained in an inner circuit disposed on the chip. A dummy transistor having a relatively short channel length is employed as a circuit for detecting the electrical characteristics of the transistors formed on the chip. The voltage drop across the dummy transistor is employed as a representative signal since it is sensitive to variations in the characteristics of the FETs contained in the inner circuit.

Abstract: An integrated-circuit analog-to-digital converter of the successive-approximation type formed on a single monolithic chip. The converter is made by a diffusion process wherein certain portions of the chip are formed with normal-mode linear transistors, and other portions are formed with inverted mode I.sup.2 L transistors. The normal-mode transistors provide a switchable current-source DAC, a set of three-state output buffers, and a comparator. The inverted mode transistors provide an internal clock and successive-approximation control circuitry for the DAC. The chip also includes a voltage reference to provide for absolute analog-to-digital conversions.

Abstract: A stabilized generator includes an operational amplifier with capacitive negative feedback whose output signal controls a current regulator which drives the input of a current mirror circuit, the mirrored current from the mirror circuit controlling a feedback circuit adapted to drive the operational amplifier in order to maintain the mirrored current constant.

Abstract: A highly stable voltage regulator circuit based on a low-voltage reference and supplying a voltage which is substantially higher than the reference voltage. The circuit is to be constructed as an integrated circuit comprising transistors of one conductivity type and without a zener diode.The reference voltage is supplied by a "band-gap reference" circuit (1). A differential circuit (T16, T17) controls the output voltage, which is applied to the base of a transistor (T16) via a resistor (R16) in which the current is maintained constant by means of an associated differential circuit (T11, T12) which comprises a resistor (R11) connected between its emitters. The bases of the transistors T11, T12 are each connected to one end of a resistor (R20) arranged in a bridge connected between the reference terminal and ground.

Abstract: A power supply 10 providing a DC output voltage comprises a voltage input circuit 11, a charge buildup and transfer circuit 14, a switch including SCR3 for selectively interconnecting the input circuit 11 and the charge buildup and transfer circuit 14, a trigger circuit including a unijunction transistor gating circuit 16 for triggering the SCR3, and a sensing circuit 22 including a current reference 26 for sensing the current output to the load 38 and comparing the output to current reference 26 while providing a comparison signal to the trigger circuit 16 so as to modify the triggering of SCR3 and thus the interconnection of the voltage input circuit 11 and the current buildup and transfer circuit 14.

Abstract: A reference voltage generating circuit has a control transistor whose collector-emitter path is connected between the output terminal and an input terminal, first and second resistors connected in series with the collector-emitter path of a current detection transistor between the output terminal and ground with the base of the current detection transistor being connected to a connection point between the first and second resistors, a third transistor whose base-emitter path is connected in parallel to the collector-emitter path of the current detection transistor and which has an emitter periphery area n times an emitter periphery area of the current detection transistor, a fourth transistor of the same conductivity type as the current detection transistor and the base of which is connected to the base of the current detection transistor, and a circuit in which a difference between the collector currents of the third transistor and the fourth transistor is detected and a corresponding signal is negatively fe

Abstract: A pair of ratioed emitter size transistors is operated to produce a .DELTA.V.sub.BE. A second pair of transistors is coupled in series with the first pair and matched therewith so as to produce 2.DELTA.V.sub.BE. This differential voltage appears across a resistor coupled in series with the low current density transistors. This circuit combination produces a current that is proportional to absolute temperature (PTAT) and which is passed through a suitable value resistor to develop a PTAT voltage. This voltage is combined with a negative temperature coefficient voltage produced by forward biased series connected diodes so as to produce a combined voltage that is a multiple of the semiconductor bandgap extrapolated to absolute zero. The diodes are operated at very low current levels so that the circuit requires a very low operating current.

Abstract: A DC-DC converter having a high conversion efficiency and stable output voltage. A constant current supply circuit, located between the output terminals of the converter, make it possible for the source current to decrease as a function of battery output voltage, resulting in lower current requirements for a lower required voltage boost and hence increased efficiency.

Abstract: The present invention achieves constant voltage at radio frequencies to drive a constant voltage to constant current converter, by employing a tightly coupled d.c. feedback loop to control the voltage via a transformer to the drain of a FET operated as a Class C amplifier in the saturated mode whereby among other advantages, the amplifier can withstand, without damage, very high VSWRs. Control is affected by a high gain differential amplifier which compares a d.c. voltage derived from the r.f. output of the system against a highly stable d.c. voltage reference. A controller, responding to the output of the differential amplifier causes a first level of voltage to be applied to the drain of the FET when the system is not loaded and causes a second voltage varying between said first level and a higher level when the system is loaded.

Abstract: A voltage-to-current converter circuit for outputting a current accurately proportional to the input signal voltage, which converter circuit includes an operational amplifier for providing an output corresponding to a difference between the input signal and a feedback signal, and includes a feedback circuit for detecting the output current in the form of a voltage by making the output current flow through the reference resistor and for feeding back the detected voltage. Further, the feedback circuit includes a polarity inverting circuit which holds the voltage detected by the reference resistor and inverts the polarity of the voltage, and then feeds back to the operational amplifier.

Abstract: A direct-current power supply for supplying electric current to a load and operable with a plurality of types of batteries includes a housing unit for loading therein batteries employed, a monitor device for monitoring a voltage output from batteries in use, an indicator for indicating a warning, a comparing device which compares the monitored voltage with a reference voltage to energize the indicator when the monitored voltage becomes lower than the reference voltage, a voltage generating unit for generating a plurality of voltages as the reference voltages associated with the types of batteries available, and a selecting unit for selectively supplying one of the plurality of voltages generated to the comparing device. Each of the plurality of voltages is set to a value higher than a limit voltage which is sufficiently low for allowing an normal operation of the load.

Abstract: A MIS semiconductor integrated circuit is one which contains an internal circuit. In the internal circuit, an externally supplied power source voltage supplied to a power source voltage terminal is supplied to the voltage input terminal of a voltage dropping circuit. The voltage at a voltage output terminal of the voltage dropping circuit is detected by a voltage detecting circuit containing an inverting circuit with a predetermined threshold voltage. The voltage dropping circuit is switch-controlled by applying the detected voltage to the control terminal thereof. The voltage output terminal of the voltage dropping circuit provides an internal power source voltage which is formed by dropping the externally supplied power source voltage. An internal circuit containing MOSFETs with an effective channel length of 1 .mu.m or less is driven by the internal power source voltage.

Abstract: An integratable load voltage sampling circuit utilizes a plurality of current-mirrors. One of the current mirrors is switched into conduction during a load-current conduction time interval, while another current mirror operates during the entire source half-cycle during which the first current mirror is pulsed to conduct. The total current from the plurality of current mirrors is summed and compared to a reference level; the difference in magnitude between the sampled and reference values is integrated, with respect to time, to provide a load conduction-angle adjustment signal having a magnitude varying as the root-mean-square magnitude of the average load voltage.

Abstract: A drive circuit for controllably driving a heater which is used for maintaining ink in an ink jet printer at a predetermined temperature. A plurality of power sources are installed in the circuit each for supplying a voltage to the heater. The power sources are selectively connected to the heater by a plurality of output transistors and an error amplifier adapted to control switching actions of the output transistors. Diodes are interposed between the respective transistors and the error amplifier to enhance the linearity of the level of the voltage supplied to the heater.

Abstract: A circuit for supplying direct current to a line (a, b) from a battery via two supply resistors (RA, RB). Part of the current supplied by the battery flows in a secondary path including a resistor (R4) and a transistor (16), and is maintained at a constant value. A symmetrical and differential resistance bridge connected between the supply resistors and the line detects the transverse alternating current flowing into the battery, and means (15) are provided to cause the transistor to generate a negative-feedback alternating current whose value is adjusted to cancel said transverse alternating current.

Abstract: A precision voltage reference comprising an IC chip having a Zener diode connected to the input of an operational amplifier. Variations in output with temperature are minimized by selectively controlling the Zener current in accordance with temperature. The current is controlled by a resistive circuit including a thermistor connected in parallel with the Zener. A method of trimming the voltage reference is provided wherein an optimum quiescent operating current is determined based on voltage and current measurements at two different temperatures.

Abstract: A highly efficient series regulator for use where output voltage may closely approach input voltage uses the channel of a field effect transistor as a series voltage-dropping element. The conduction of the channel of the field effect transistor is controlled without consumption of appreciable power in the control circuitry for the transistor. Presently available power field effect transistors are of p-channel enhancement mode type. Their threshold voltages are sufficiently high as to make difficult the closing a d.c. feedback loop as will allow output voltage to approach closely input voltage. This problem of closing the d.c. feedback loop is overcome by using voltage boost circuitry, powered from the input voltage supply to the regulator, against which to refer the error signal applied to the gate electrode of the field effect transistor.

Abstract: An integrated precision reference source for supplying a reference voltage or a reference current under the condition of a lower feed voltage is disclosed, includes a first transistor, a first resistor connected between base and collector of the first transistor, a second resistor connected between base and emitter of the first transistor, and a second transistor whose base is connected to the collector of the first transistor and whose emitter is connected through a third resistor to the emitter of the first transistor.

Abstract: An integrated-circuit analog-to-digital converter of the successive-approximation type formed on a single monolithic chip. The converter is made by a diffusion process wherein certain portions of the chip are formed with normal-mode linear transistors, and other portions are formed with inverted mode I.sup.2 L transistors. The normal-mode transistors provide a switchable current-source DAC, a set of three-state output buffers, and a comparator. The inverted mode transistors provide an internal clock and successive-approximation control circuitry for the DAC. The chip also includes a voltage reference to provide for absolute analog-to-digital conversions.

Abstract: Disclosed is a line interface circuit (103) having a negative feedback circuit (205) for maintaining the DC voltage on an electrically isolated communications line at a reference level such as ground for private branch exchanges using ground start supervisory signaling. The feedback circuit comprises a low-pass filter (301), a difference amplifier (302), and two voltage-to-current sources (303,304) each having a high output impedance. The low-pass filter passes only the voltage on the line below a predetermined frequency. The difference amplifier subtracts the passed voltage from a ground reference level to form a difference voltage. Depending on the polarity of the difference voltage, the two voltage-to-current sources source and sink current to and from the line to maintain the DC voltage on the line at the reference level.

Abstract: A low voltage series pass regulator configuration has an input terminal for receiving a predetermined input voltage and an output terminal operatively connected to a load. The regulator comprises at least one field effect transistor in a source follower configuration. The drain of the field effect transistor is operatively connected to the input terminal and the source is operatively connected to the output terminal which provides an output voltage across the load. In one embodiment of the present invention a current limiter is operatively connected between the source and a gate of the field effect transistor. In another embodiment of the present invention a comparator for comparing the output voltage to a first reference voltage is provided. The comparator supplies a control voltage, indicative of the value of the output voltage compared to the first reference voltage, to the gate of the field effect transistor.

Abstract: A floating precision current source circuit comprising: a voltage source means referenced to a reference potential, such as ground, for providing at least one precision voltage reference, and a floating first means for generating a precision unipolar current, the floating first means being responsive to the precision voltage reference and having: a current source terminal, and a current sink terminal; the floating first means being characterized as sourcing the precision unipolar current to the current source terminal and sinking the precision unipolar current from the current sink terminal; load switching means for coupling the current source terminal at a first potential to the load terminal at a second potential; the floating first means being further characterized as controlling the value of the precision unipolar current from the current source terminal, through the load switching means to the load terminal, the precision unipolar current value being relatively independent of the current source terminal

Abstract: A band-gap voltage reference circuit which incorporates a band-gap differential amplifier supplied with constant, temperature-independent current, a high gain differential-to-single-ended converter, temperature-compensated negative feedback means and a common source of biasing to serve as a device to provide an output reference voltage so that the output reference voltage is precise and independent of variations in temperature, loading and power supply voltage. An improved amplifier is also disclosed.

Abstract: A motor control apparatus for driving and controlling a motor, in which a signal frequency proportional to a rotation number of the motor is converted into a d.c. voltage by a frequency/voltage converter so as to drive and control the motor by the d.c. voltage.

Abstract: A two-terminal current regulator has a sensing resistor, a reference voltage generator, a current controller, an error amplifier for controlling the current controller such that a voltage drop across the sensing resistor is equalized to a reference voltage generated by the reference voltage generator, and a current distributor for distributing currents to the reference voltage generator, current controller and the error amplifier such that the currents are proportional to a current flowing through the sensing resistor. Thus, a high precision constant current characteristic is attained.

Abstract: The invention relates to a device particularly adapted for use with the power supply of a computer for controlling the regulating facilities in an electric high-power AC-DC converter of the power supply.This control device (D) comprises a regulation (CC) control comparator connected to the storage facilities (S) of the converter and receiving a reference voltage having a "nominal" value when the converter is normally powered by an AC network and receiving a portion of the output voltage from the converter, the output of said control comparator (CC) supplying an error signal to the regulating facilities (MR) of the converter. The control device also includes facilities (R) for supplying a variable reference voltage to the control comparator (CC) so that at the moment of recovery of the network following a cutoff, the voltage at the input of the filtering facilities (F) of the converter is, at the most, equal to the output voltage of the storage facilities (S).

Abstract: An electronic timepiece having voltage regulation, temperature detection and battery voltage detection means provided on the same integrated circuit as is used for timekeeping circuitry, and having external terminals for stepwise weighted adjustment of timekeeping gain/loss.

Abstract: A circuit for providing a current at an output thereof of a predetermined value which has excellent ripple rejection characteristics whereby the magnitude of the current is maintain substantially constant with variations in the voltage supply applied thereto. The current source includes first and second complementary current mirror circuits interconnected such that the second current mirror sinks the current sourced from the first current mirror. A feedback loop latches the circuit into a stable operation and senses any difference current between the two current mirror circuits caused by perturbations of the supply voltage to produce feedback to maintain the circuit at its quiescent operating point.

Abstract: A voltage divider circuit is provided which can be fabricated as a portion of a monolithic integrated circuit without requiring any external capacitors. The voltage divider circuit has a pair of capacitors which are alternately switched between series connection and parallel connection to divide an input supply voltage. The voltage divider circuit can thereby provide a second supply voltage of one half the input supply voltage.

Abstract: A motor drive circuit for a camera which circuit is adapted to control a motor which is incorporated in a camera body, a film winder, a lens cylinder body or the like. The function of such a motor is to carry out film winding and rewinding, shutter charging and actuation of a taking lens for focusing or other photographic operations. The motor drive circuit is provided with a battery for supplying electric power to the motor and is arranged to control a motor driving current which is supplied to the motor and a control current which is not supplied to the motor but is used to control the motor driving current, so as to raise the efficiency of the use of the battery, i.e., to bring about longevity of the battery.

Abstract: A precision voltage and current source for use, for example, in a transceiver for a carrier-sense multiple access communications network using collision detection wherein the use of one or more precise threshold voltages is required. The threshold voltage(s) is (are) created by a current source which pulls a current through a precise resistive load to yield a precise voltage. A power supply with regulated voltage drives the current source. A feedback voltage from the current source, proportional to the output current of the source, is compared with a reference zener diode voltage; the difference, or error, voltage controls the regulator to drive the regulated power supply voltage in the direction which drives the error voltage to zero. The precise resistive load is preferably formed of two resistors in series. A first threshold voltage is developed across one resistor, corresponding to the average signal level required for receiving signals on the network.

Abstract: A power circuit for an electronic wristwatch is provided wherein voltage reduction circuit means is positioned intermediate a battery source and at least a portion of the circuitry of the timepiece to be driven by the battery source. The battery source is preferably a lithium battery. The voltage reduction circuit means include a capacitor and other circuit components formed on an integrated circuit substrate.

Abstract: A voltage regulator circuit adapted to operate between a voltage source and a voltage source return, to supply a predetermined output voltage at an output voltage terminal to a load comprising: a voltage reference means for supplying a reference voltage approximating the desired output voltage, an output voltage scaling means providing a scaled output voltage signal, an amplifier means having a first input, responsive to said reference voltage, a second input, responsive to said scaled output voltage signal, said amplifier amplifying the voltage difference between said first and second inputs to provide an output voltage determining control signal, an output multiterminal semiconductor device having a first and second conduction path terminal and a control terminal, said first conduction path terminal being connected to said voltage source, said second conduction path terminal being connected to said output voltage terminal, said control terminal being responsive to said control signal to provide current to s

Abstract: A temperature stabilized voltage reference is generated based on the difference in the base to emitter voltages of a pair of transistors operating at different current densities which is summed with a voltage that is a predetermined fraction of one of the base emitter voltages. This voltage is utilized to provide for a constant current through a load by adjusting the current through a sense resistor to the value of the temperature stabilized voltage.

Abstract: A temperature-compensated reference voltage circuit includes a transistor having a positive temperature coefficient of current. A circuit for establishing a predetermined current in the positive-temperature-coefficient-of-current transistor is connected to that transistor. A predetermined resistance serially connects the positive-temperature-coefficient-of-current transistor with a transistor having negative temperature coefficient of base-to-emitter voltage. The temperature-compensated reference voltage is established between the transistors. The temperature-compensated reference voltage circuit is particularly useful in a supply voltage sense amplifier circuit for thermal printhead drive transistors or other load elements. The sense amplifier circuit includes a circuit for comparing the reference voltage and a supply voltage. An output is adapted to be connected to a load for receiving the supply voltage.

Abstract: The output from a reference voltage source is provided to a DC amplifier and its output is applied as a reference voltage to an output terminal. The output thus derived at the output terminal and the output from the reference voltage source are changed over by a switch to be alternately supplied to a smoothing circuit, the smoothed output from which is fed back to the DC amplifier. The switch is changed over periodically by a control signal from a control circuit, and by controlling the change-over ratio of the switch, a reference voltage of a desired value is provided at the output terminal. Thereafter, when the output voltage at the output terminal deviates from the reference value, the deviation is corrected by the feedback action.

Abstract: An output voltage-drop detecting apparatus added to a stabilized DC power source device which includes a power control circuit for controlling a DC input voltage to produce a DC output voltage of a specified value, a reference voltage source whose voltage is capable of being varied, and an error amplifier, with the DC output voltage and the reference voltage being compared by the error amplifier and the power control circuit being controlled by the output of the error amplifier to stabilize the output voltage.

Abstract: The exemplary embodiments concern reference sources for A/D and D/A converters, for example of a PCM telephone exchange system. Two separated stages which are supplied however from the same direct current supply source, contain in each case the series circuiting of at least one IG-FET and at least one load resistor. Between the taps of the stages, a differential voltage appears, which is used itself directly as a reference voltage, or indirectly is used for the setting of the value of a reference voltage, or of a reference current, for example by a voltage divider. The value of the reference voltage, or of the reference current, is also exactly adjustable after production of integrated modules, because in at least one of the two stages, at least one of the IG-FETs contains a memory gate which is at least partially applied between the controllable control gate and the channel area, is on all sides surrounded by an insulator, and thus is floating in the electrical sense.

Abstract: A plurality of metal resistance elements and a metal resistance element for compensation use are formed on a common substrate and placed under the same temperature condition. A reference current is applied to the metal resistance element for compensation use to yield an auxiliary reference voltage. A plurality of switches are individually connected in series to the reference metal resistance elements and the auxiliary reference voltage is provided to the series circuits to selectively control the switches, thereby obtaining various currents.

Abstract: A voltage regulator for use in photovoltaic charging of storage batteries includes a temperature compensated reference voltage. The circuitry of the invention permits fixed temperature coefficient and variable temperature coefficient temperature compensated regulation.The voltage regulator comprises an operational amplifier including a linearly temperature dependent current source coupled to an input terminal of said operational amplifier and a voltage source having a selectable voltage which is connected to another input of said operational amplifier, said reference voltage circuit being operable to provide a reference voltage about equal to a maximum charging voltage for said batteries;a comparator for comparing said reference voltage with an output voltage of said photovoltaic array; anda switch responsive to said comparator to inhibit charging whenever said array output exceeds said reference voltage.

Abstract: An improved band gap voltage regulator provides a stable, temperature-independent, output voltage which is approximately equal to the band gap voltage of silicon or a function thereof. The circuit utilizes integrated circuit resistors and bipolar transistors. Semiconductor process variations which affect transistor base-emitter junction voltage and thus would otherwise affect the value of the output voltage are compensated by a base pinch resistor.

Abstract: A system for generating and autocontrolling the voltage or current wave form in a process for the electrolytic coloring of anodized aluminium includes feeding power from a source of symmetrical direct current, with a neutral connection directly coupled to a load, while the positive and negative voltages supplied by the source pass through a power control stage which is controlled by a bipolar operational amplifier. The bipolar operational amplifier has two signal inputs, a positive or non-inverting input which is connected to a signal generator, and a negative or inverting input having a signal which corresponds to the signal which actually exists on the electrodes of the electrolytic bath. This signal is processed in a half-wave outer controller which is controlled by a programming system.

Abstract: A circuit is coupled to an external power supply and is coupled to a non-live zero, two wire DC current transmitter (e.g. 4-20 MA output) for converting such current to a live-zero DC output current signal (e.g. 0-20 MA output) and for powering such transmitter. The circuit has a first current to voltage converter for converting the transmitter current signal to a voltage signal, and a second current to voltage converter coupled to receive the circuit output current signal and an offset current from an offset current source for converting the sum of the circuit output and offset currents to a second voltage signal. A comparator is used for comparing the first and second voltage signals to provide the live-zero output current signal representative of the non-live zero transmitter signal. The circuitry can also provide isolated power to the transmitter and feedback (closed loop) control of such power.