Abstract: An RF power amplifier is operated by supplying an RF signal to the amplifier for amplification and thereby providing an output RF signal to the amplifier's output circuit which has an impedance matching output network connected in series with a load. A detector serves to detect any reflected power in the output circuit. The RF power amplifier is turned off when the detected RF power exceeds a reference level. The amplifier is protected by discontinuing the supply of the RF signal to the amplifier while it is turned off and, instead, a frequency signal is supplied to the RF amplifier having a frequency that corresponds with that of any current flowing in the output circuit.

Abstract: A circuit for protecting electronic devices which are fed from a source of dc voltage and to which a subscriber's line (ASL) is connected. In order to limit the current in the event of an overload on the subscriber's line (ASL), a MOSFET (T1) is provided as current-limiting component. The MOSFET (T1) is disconnected and re-connected periodically by means of a relaxation generator (K) when the MOSFET is in its current-limiting condition. Upon the normal operation of the circuit, the relaxation generator (K) does not operate. By proper dimensioning thereof, the time for which the MOSFET (T1) is blocked can be roughly adjusted as compared with the time in which it acts as current limiter. In this way, too great a heating of the MOSFET (T1) is avoided.

Abstract: A stand-by signal is supplied to a stand-by circuit for determining the operation condition is a normal operative mode or a stand-by mode to control the operation. An output signal of the stand-by circuit is delayed by a delay circuit. An output signal from the delay circuit is supplied to a bias circuit for generating a predetermined bias voltage. An audio signal supplied from the audio signal input terminal is amplified by an amplifier circuit based on the bias voltage from the bias circuit. When it is detected by an overcurrent detection circuit that an overcurrent flows in the amplifier circuit, supply of the bias voltage from the bias circuit to the amplifier circuit is interrupted by the protection circuit. The operation of the protection circuit is controlled by output signals from the delay circuit and the overcurrent detection circuit.

Abstract: A transistor is protected from excessive power dissipation in the event of a shorted load condition by alternately turning the transistor off for a relatively long period of time during which a capacitor is discharged through a resistor network and turning the transistor on for a relatively short period of time during which the capacitor is charged through a diode by the voltage developed across a resistor connected in circuit with the transistor.

Abstract: The present invention relates to a device for use in an amplitude modulated RF transmitter. The device protects power transistors located in the RF transmitter particularly in the modulator and power amplifier portions of the transmitter. The device is comprised of a capacitor unit which is adpated to be charged in a first direction; a detector which detects an audio modulating signal; and a discharge unit which is connected to both the capacitor unit and the detector which selectively discharges the capacitor unit when the value of the audio modulating signal reaches a first preset level for a preset time duration during a portion of the audio modulating signal which causes positive modulation of the RF transmitter. The device also comprises a switch unit connected to the capacitor unit and which is activated when the capacitor unit discharges to a predetermined level. The switch unit is operable to remove, when activated, the audio modulating signal from the power transistors.

Abstract: An integrated circuit has an input protection circuit coupled between an input pad and an input circuit. The input pad receives a signal provided externally from the integrated circuit. The input circuit is responsive to the signal provided externally from the integrated circuit. The input protection circuit provides protection against electrostatic discharge (ESD). The input protection circuit includes two polysilicon resistors in parallel in which one has a greater width than the other. The greater width resistor will be the first to open under ESD stress leaving the other resistor to still provide a signal path between the input pad and the input circuit.

Abstract: To permit cooling of transistor push-pull bridge-type audio end stages in car radios, where heat dissipation and cooling of components is difficult to achieve, without entire interruption of signals being amplified, the temperature of a heat sink (HS) is being sensed by a temperature sensor (14), and, if a predetermined level is exceeded as determined, for example, by a threshold circuit (15), one of the bridge arms formed by a transistor (10) is controlled to become saturated, thereby grounding-out the applied signal, so that a loudspeaker (6) will operate at only half voltage and hence 1/4 power, to thereby permit cooling of components, while providing some reproduction of introduced audio signals from an audio input terminal (11).

Abstract: A composite transistor device having over-current protection is disclosed, and particularly a device for protecting Darlington configuration power transistor devices. The over-current protection circuit operates to clamp the base-emitter potential of the exciter transistor thus causing the power output transistor to maintain a power output below a predetermined threshold value. This allows the control of the power output intensity so as to avoid damage to the circuit, and with a minimum of power losses due to active voltage losses.

Abstract: A short circuit limiter having at least one current sink transistor connected to a trip point voltage setting resistor. The trip point voltage setting resistor receives a current which is a function of a reference current. One of the current sink transistors has a base connected above the tip point voltage setting resistor. The emitter of one of the current sink transistors sets the trip point voltage and is connected to the output transistors. If there is a short circuit in a load, the increased current will cause the voltage connection between the output transistors and the current sink transistors to rise up to the trip point voltage at which point, base drive current will be diverted away from the output transistors and through the current sink transistors.

Abstract: A monolithic integrated circuit (IC) chip in which is formed a multi-driver power circuit, with each driver circuit including one output power transistor, is partitioned such that the power transistor of each driver circuit, formed in the IC, is spaced apart from those of any other driver circuit a distance sufficiently large to ensure the generation of a temperature differential between the power transistors of the different driver circuits when their power dissipation is different. A thermal sensor is formed in close proximity to each output power transistor, and as far away as possible from the other power transistors of the IC, whereby each thermal sensor is thermally, tightly, coupled to its associated power transistor. Each thermal sensor is electrically coupled to the base of its associated power transistor for controlling the conductivity of its associated power transistor when the power dissipation of its associated power transistor and its resulting temperature exceeds a predetermined level.

Abstract: A class A bridge topology for audio amplifiers configured to operate in constant current mode, comprising power stages (3,4,5,6) supplied by supplies (8,9) and driven to equal amplitude opposite phase output signals applied across a load (7). Symmetrical current conditions are placed on said power stages to achieve a cancellation of supply currents during signal application to the load. Supplies are current limited to afford non-intrusive protection against overstress.

Abstract: A circuit arrangement protects against thermal overload as a consequence of impermissible operating conditions in traveling wave tube amplifiers having multi-collector traveling wave tubes. At least one measuring device is provided for measuring the collector current at at least one collector of the traveling wave tube and, in response to measuring a prescribed current threshold, the cathode current of the traveling wave tube is regulated back by way of a control device or is disconnected by way of a control logic circuit.

Abstract: An audio amplifier of the type including circuitry to detect clipping and adjust the gain of an amplifier input element to control the clipping in closed loop operation further includes circuitry effective to sense the temperature of an amplifier component and change the amplifier bias voltage that determines the maximum non-clipping voltage so as to induce clipping in the amplifier when the temperature exceeds a predetermined temperature. The clipping control circuitry then reduces the input gain to the amplifier to control the clipping and, in so doing, reduces power dissipation to a level allowing the temperature to decrease to the predetermined temperature. The circuit provides for closed loop control of amplifier temperature in marginal temperature situations with minimal intrusion on the music reproduction process.

Abstract: An improved power controller and protection circuit to regulate the RF output power of a radio transmitter and to protect its RF amplifier from overload damage. The controller features a floating input, voltage controlled current source with high common-mode rejection to provide feedback of the DC input current drawn by the RF power amplifier. The controller can use an arbitrary reference voltage, which allows its application universally with power amplifiers designed for different rated output powers and frequency ranges.

Abstract: A protection circuit is provided for a planar transistor device. The protection circuit comprises a variable resistor device formed of a junction type field effect transistor. The resistor device is connected in series with the base of the planar transistor. The drain electrode of the J-FET is connected to the base of the planar transistor while the collector of the planar transistor is connected to the gate of the J-FET. Due to this interconnected scheme, base input resistance of the planar transistor is increased to reduce its base current when a high voltage is applied accidentally to the collector. The base current is not eliminated, however, and the device is protected but can still operate.

Abstract: A device is disclosed for protecting against shorts the transistors of the push-pull stage in a power amplifier operating on a low voltage supply, in particular for car radio sets. The device comprises sensors which are responsive to currents flowing through the two transistors which form the amplifier push-pull stage, and current-to-voltage converters which convert the sensed currents into corresponding respective voltage signals. The latter are compared in respective voltage-comparing circuits with a reference voltage indicative of the highest admissible current through either of the transistors while the other is shorted. The device also comprises two additional voltage comparators wherein the voltage applied to the load, which may be of a resistive or a reactive type, is compared with a set reference voltage which is lower than or in the extreme equal to, in absolute value, the voltage supply to the amplifier push-pull stage.

Abstract: A semiconductor integrated circuit device comprising: at least two NPN transistors whose bases and emitters are connected to the ground and whose collectors are connected to an input terminal; one of said NPN transistors having a lower breakdown starting voltage and a higher breakdown maintaining voltage than those of the other of said NPN transistors; and an input portion which has a breakdown maintaining voltage at a high surge voltage breakdown which occurs caused by an application of a high surge voltage input to said input terminal which is lower than that at a low input voltage breakdown which occurs caused by an application of a low surge voltage or an input voltage which rises up gradually.

Abstract: A power circuit comprises a current amplifier circuit connected between a minimum potential line and a maximum potential line. It further comprises, connected between these lines together with the aforementioned main circuit, a protection circuit which has a control input. A trigger and distributor circuit is connected in parallel with these circuits and is adapted to neutralize the protection circuit, via its control input, when the voltage across the main circuit is below a threshold value. Is it also adapted to activate the protection circuit when the voltage across the main circuit reaches this threshold value, while maintaining the voltage across the main circuit at an approximately constant ratio to the voltage between the two potential lines. The circuit is applicable in particular to controling failsafe alarm circuits, by means of logic signals, for example.

Abstract: An apparatus for controlling the output power of a transmitter that is installed in a vehicle or used in a mobile radio communication equipment has a power amplifier, a coupler for delivering an output corresponding to the output power from the power amplifier, a detector disposed after the coupler, a comparator for delivering an output proportional to the difference between the output voltage from the demodulator and a reference voltage, and a voltage control circuit for controlling the output power of the power amplifier in response to the output from the comparator. An RF variable attenuator is disposed before the comparator to compress the dynamic range of the signal applied to the voltage control circuit.

Abstract: A battery-powered radio communication apparatus is disclosed which comprises a power amplifier and a power detector for detecting the output power of the power amplifier. A supply voltage detector compares a standard voltage with the output voltage of a battery supplying power to the power amplifier. A gain control circuit controls the gain of the power amplifier in response to the output of the power amplifier and to the output of the supply voltage detector so as to prolong, by a certain time, the communicable state of the apparatus prior to battery depletion.

Abstract: A monolithically integrated, polarity-reversal protected switching circuit includes, in the output of a switching stage, a symmetrical thyristor instead of an otherwise customary diode. This thyristor is constituted by an npn transistor and a lateral pnp transistor. The control input of the thyristor is controlled by an additional control arrangement in such a manner that the thyristor is switched off at the occurrence of high voltage peaks. In this manner, there is obtained a relatively inexpensive monolithically integrated switching arrangement which is protected against polarity reversal and withstands voltage pulses of up to 150 volts.

Abstract: An audio power amplifier employs highly linear power MOSFET gain circuitry that uses distortion cancellation rather than negative feedback to maintain high linearity and to greatly reduce transient intermodulation distortion.

Abstract: A short circuit protection device for a unitary voltage gain signal transducer circuit (G.sub.v) and for a load impedance (R.sub.L) coupled to the transducer circuit includes a first (A.sub.1) and a second (A.sub.2) threshold comparator circuit and an actuator circuit (ACT). The input terminals of the first comparator (A.sub.1) are coupled to the transducer circuit input and output terminals and the output terminal of the first comparator is coupled to an activation terminal of the actuator circuit. The input terminals of the second comparator (A.sub.2) are coupled to the ends of the load impedance and the output terminal is coupled to an inhibit terminal of the actuator circuit. A first output terminal of the actuator circuit is coupled to an inhibit terminal of the transducer circuit, while a second output terminal of the transducer circuit is used to deliver a small current I.sub.1 to the load impedance.

Abstract: An output circuit which has an improved protection circuit against an abnormal voltage applied to an output terminal. The output circuit is of the type having first and second switching transistors operating in a push-pull manner, the output being derived from the intermediate connection of the first and second switching transistor. A protection circuit is coupled between a gate of the first switching transistor and the output terminal. The protection circuit provides a current path between the gate of the first switching transistor and the output terminal when an abnormal voltage is applied to the output terminal.

Abstract: An output transistor of an RF power amplifier remains stable so that it does not generate subharmonic spurious outputs. An adaptive stabilization network maintains the stability of the output by decreasing the impedance presented to the output transistor when voltage levels at the output transistor exceed a predetermined level. A combination consisting of a peak detector coupled to a Zener diode senses the predetermined level. A PIN diode couples to the Zener diode and to the output transistor so that the PIN diode becomes forward biased when the predetermined level is exceeded.

Abstract: A local computer network transceiver is provided for a distributed control local computer network which applies a signal to a medium which has a DC component wherein isolation is implemented at the medium interface without need for direct current coupling of any active circuit to the communication medium. The medium is typically a coaxial cable. Transmit isolation transformers are coupled across a coaxial coupler, the medium side thereof being coupled in series with a diode. A plurality of transmit isolation transformers may be coupled in parallel to the medium to permit operation at substantially higher frequencies than would otherwise be permitted due to self-resonant frequencies of the isolation transformers. A receive interface through a receive isolation transformer is provided with capacitive balancing to prevent common mode voltages from being converted into recognizable signals.

Abstract: An adaptive impedance mismatch detector system is provided for determining whether or not a particular load impedance is matched or mismatched to the characteristic impedance of a transmission line. The detector system is capable of determining if a particular load impedance has a value outside of an impedance threshold circle having a center at a location other than at the center of the Smith Chart. The system changes the radius and/or center of the threshold circle in response to changes in circuit operating conditions or parameters. This flexibility enables the detector to be more selective in determining improper load conditions.

Abstract: A method of fault sensing for a power amplifier having direct coupled power stages with normally mutually exclusive current flow in which the alternating current output is simultaneously sensed and, when a fault is detected, is ANDed. A power reduction to the amplifier is initiated when the ANDed output exists for a selected period of time.

Abstract: Input/output circuitry is disclosed for use in an I/O system of a programmable controller. The circuitry is protected against overcurrents without the use of fuses or circuit breakers, and is automatically restored to normal operation following correction of an overload condition. Diagnostic signals are produced for monitoring the operating condition of the circuitry. The invention includes an insulated gate transistor (IGT) having a main current section carrying a majority of the load current and an emulation section which carries a fractional portion of the load current. The emulation section current tracks the total current at all times. A current sensor monitors the emulation section current and provides a signal representing the instantaneous load current. This signal is continuously compared with preselected reference levels to derive a set of diagnostic signals that are indicative of the operating condition of the circuit, and whether output loads are open or shorted, for example.

Abstract: A circuit for the commutated turn-off of latched power switching devices, such as of the insulated-gate transistor/insulated-gate rectifier type, monitors the gate drive voltage and a load-current-related parameter (e.g. the collector/anode voltage) of the at least one power switching device connecting a load to a source. Comparator outputs provide logic signals indicating whether the at least one switching device has latched or has turned off in normal manner, responsive to cessation of gate drive. Circuitry for providing a cyclic gate drive signal is enabled whenever a latched condition is detected. The cyclic signals occur until the latched device is actually turned off, at a driven-unlatching current typically one-half the device latching current and typically at least an order of magnitude greater than the current at which the device will undergo self-unlatching turn-off.

Abstract: A bridge amplifier having paired high and low output stages in which a main amplifier receiving an input signal drives the high output stages and a balancing amplifier drives the low of the output stages. A junction temperature simulation circuit extends between the main amplifier and the low output stages in which the temperatures of the low output stages are sensed to produce an arresting of the main amplifier drive to the high output stages and thereby simultaneously control the balancing amplifier and its drive to the low output stages.

Abstract: A protection circuit for a power amplifier in which feedback is applied from the output to the inverting input of the amplifier by a negative feedback network comprising a first resistor, a second resistor and a capacitor, comprises a voltage-current converter whose input is connected to the output of the amplifier which is loaded by a load and whose output is connected to the junction point of the second resistor and the capacitor. When the protection circuit is activated if the output transistors of the amplifier are loaded excessively for example due to short-circuiting of the load, the input voltage of the voltage-current converter, for low frequencies, is converted into a current which is re-converted into a voltage in the capacitor, which voltage is added to the normal negative-feedback voltage provided by the voltage divider comprising the first resistor and the second resistor. This provides a strong negative feedback and hence a satisfactory protection.

Abstract: The output of a deflection operational amplifier is coupled through a dissipation circuit to a deflection yoke coil of a stroke written cathode ray tube for deflecting an electron beam on the tube screen. A feedback circuit is coupled between the coil and the inverting input of the amplifier to control the current through the coil. The dissipation circuit comprises a dissipative resistor, such as an incandescent lamp, and a shunt connected bypass capacitor. The dissipation circuit dissipates power during coil steady current conditions such as exist during slow movement or hold of the electron beam on the screen when voltage across the coil is low but coil current may be high. Thus the power otherwise dissipated in the amplifier output transistors is dissipated in the dissipation circuit. The bypass capacitor passes high frequency deflection signals to the coil during coil high instantaneous current conditions corresponding to fast movement or slewing of the electron beam on the tube screen.

Abstract: A protection circuit for a push-pull amplifier includes two sensing transistors arranged in respective feedback circuits. The output signals of such sensing transistors, which are indicative of the output voltage, are used to limit the output current of the amplifier in such a manner that the output current is limited to a first threshold decreasing with a steeper slope as a function of the output voltage of the amplifier between predetermined two output voltage values, and a second threshold decreasing with increasing output voltage at a lesser slope above the higher one of the two predetermined output voltage values. This characteristic response can be overridden by appropriate circuitry so long as the temperature of the amplifier is below a predetermined maximum value, so as to make the output current threshold independent of the output voltage.

Abstract: A deflection circuit for a television includes two semiconductor switching elements connected in series. Separate control circuits are provided for each semiconductor switching element to control the operation of the respective switching element. Each control circuit receives a control signal and is connected to a voltage source. For the control circuit associated with the switching element which receives the highest voltage, connection to the voltage source and the control signal is through diodes which provide common mode isolation. This control circuit includes a capacitor which provides energy for the control circuit when the diode connecting it to the voltage source is reverse biased.

Abstract: A short detection circuit and method for operatively controlling current in an electrical load such as an alternator field coil includes a driving device such as a Darlington transistor for driving the electrical load. Detecting means selectively withhold and provide operating current to the driving means when a shorted and not shorted condition of the electrical load is respectively detected at the driven terminal of the driving device.

Abstract: An amplifier arrangement includes a first section and a second section. The second section has an output transistor which is protected by a protection circuit. The protection circuit acts on the input of the second section in order to obtain a higher gain in the protection loop. In order to preclude instabilities, the protection circuit has a falling frequency response with a flat portion in view of the frequency compensation of the second section.

Abstract: A pair of MOSFET power transistors are connected in a push-pull configuration to drive a tapped transformer and a load. A pair of diodes and an energy coupling circuit containing a capacitor and resistor in parallel bias the transformer primary in such a manner as to limit transients in a nonconducting MOSFET when the other MOSFET is conducting, aided by a drop in voltage at an inductor (ferrite bead) network which develops at the moment of MOSFET transistor conduction. This is due to a momentary change in the impedance ratio.

Abstract: Disclosed is a load impedance detector for detecting a variation of the load impedance of a single-ended push-pull amplifier having a pair of first and second transistors, the emitters of which are interconnected by a pair of series-connected first and second resistors forming a first node to which the load impedance is connected. Third and fourth resistors are connected in series to the emitter of the first transistor to form a bridge circuit with the first resistor and the load impedance so that the third and fourth resistors define a second node therebetween. A voltage difference between the first and second nodes is detected by a differential circuit which is responsive to there being a simultaneous presence of a first state in which the detected voltage difference is higher than a first predetermined value and a second state in which the potential across the load impedance is higher than a second predetermined value for generating an output signal.

Abstract: A monitoring device in integrated drive amplifiers intended to be driven by digital signals includes fault detection circuits giving a fault signal for such as excess temperature, overcurrent, or interruption and shortcircuiting in the load circuit. The input of the drive amplifier is connected to the output of a D-type flipflop (13) having a data input (D) and a clock input (C) intended for connection to a digital control system. Between the data input (D) and a potential corresponding to a logical ZERO there is connected a circuit (22,23) adapted for connecting the data input (D) to said potential during the interval between the operation signals when a fault signal is present.

Abstract: There is disclosed a power amplifier which is useful in broadband systems having load impedances with VSWRs up to a range of 2:1 or 2.5:1. The power amplifier is constructed to change its operating conditions to match the load as presented at the output of the amplifier and is particularly useful in systems employing frequency hopping requiring broadband construction. A feedback signal from the output of the amplifier is constructed to provide a signal representing the difference between forward and reflected power which is compared in a multiplier with a signal representing current flow in the power amplifier to produce a control voltage for adjusting the supply voltage of transistors forming the power amplifier. Thereafter, if the load impedance changes, the supply voltage is also changed to minimize dissipation and maintain the efficiency of the amplifier substantially constant.

Abstract: A general purpose, short circuit protector/controller circuit for drivers and amplifiers which is external to the internal circuit of the driver amplifier, which is arranged to drive a load such as electronic instrumentation. In this circuit, current sensing resistors are placed in both the positive and negative power supply input lines to the amplifier, and the voltage across each of the current sensing resistors is monitored independently for an overload condition. The voltage across each current sensing resistor is proportional to the current therethrough which drives the load, and is compared to a reference voltage, which is an equivalent representation of an overload or short circuit limit. When the sensed voltage across either resistor is greater than the reference voltage, the amplifier is tri-stated (disconnected from the load). In the preferred embodiment the amplifier is tri-stated for a period T.sub.OFF, protecting the amplifier, and is subsequently reconnected to the load for a period T.sub.ON.

Abstract: An amplifier comprises an amplifier circuit for amplifying an input signal and a supply voltage detector for controlling the operation of the amplifier circuit. The supply voltage detector has hysteresis characteristics as to a first threshold voltage and a second threshold voltage which are different from each other in order to detect the magnitudes of the supply voltage. The amplifying operation of the amplifier circuit is controlled as to the start-up and turn-off operation thereof by an output signal of the supply voltage detector.

Abstract: An output transistor protection circuit in a power amplifier comprises a limiter circuit which limits a collector power dissipation of the output transistors to a predetermined magnitude in accordance with an output voltage level of the amplifier and a current level of the output transistors. For sure limitation operation with a low cost construction, and without destruction of signal waveform, limitation characteristics of the limiter circuit is varied in accordance with detection results of an output voltage level detection circuit which detects whether the output voltage level is smaller than a predetermined magnitude, and a clipping condition detection circuit which detects whether an output stage of the amplifier is clipped.

Abstract: A protective circuit for a switching transistor is disclosed in which the base-emitter voltage of the switching transistor is compared in a comparator with a reference voltage. If the collector current of the switching transistor increases, the base-emitter voltage also increases, with the base current remaining constant. As soon as the base-emitter voltage exceeds the reference voltage, a signal is delivered at the output of the comparator. A switching-off device for switching off the driving pulses of the switching transistor responds to this signal so that a switching-on pulse present at the base of the switching transistor is switched off. The reference voltage is fixed so that the switching transistor is protected against overload by excessively large collector currents.

Abstract: A protection circuit for a switching power amplifier comprises a first detection circuit which detects a current flowing through an output stage switching circuit, a second detection circuit which detects an output voltage of the output stage switching circuit, and an amplitude limitation circuit which limits the amplitude of an input signal to the output stage switching circuit in accordance with both the first and second detection. Thus the switching circuit is surely protected from destruction.

Abstract: Two output transistors constituting a push-pull output amplifier circuit are connected in series between a power supply and a grounded point, and an output terminal is disposed at a point where the two output transistors are commonly connected. An operation detector circuit detects the operation of one output transistor. A level detector circuit detects a d-c voltage level at the output terminal. The two output transistors are driven by a drive circuit in a push-pull manner. The output of the operation detector circuit and the output of the level detector circuit control the drive circuit via a control circuit. When the operation detector circuit detected the fact that the operation of one output transistor has deviated beyond a predetermined detection level, the control circuit works to confine the operation of the abovementioned output transistor within a predetermined restriction level via the drive circuit. The power loss in the restriction level is smaller than the power loss in the detection level.

Abstract: The output of an amplifier for driving capacitive loads is protected from short circuits or other fault conditions without need for mechanical circuits interruptive devices.

Abstract: An overload protection circuit for an electrical signal source is disclosed in which an overcurrent in the signal source is sensed and the source is disabled for a predetermined time interval. If the overcurrent condition persists beyond the predetermined time interval, the turn-off cycle is repeated. The system is immune to overcurrent transients and the amplitude of the current which triggers turn-off, as well as the length of the predetermined time interval, may be selectively set.

Abstract: A circuit for supplying first and second currents to a load comprises two current generators for providing those currents during first and second time intervals and a resistance through which those currents flow. Two control potentials developed by two semiconductor junctions are applied across the resistance. First and second control circuits control the two current generators so that the first and second currents are provided during the first and second time intervals, respectively. The current supply circuit is useful in a multivibrator wherein the timing capacitor thereof is the load to which the first and second currents are supplied.