A single-ended/push-pull converter with an input emitter-follower transistor having a d.c. blocking emitter impedance and a collector impedance. The signal voltage across the collector impedance produces a signal current of opposite phase in a second emitter follower transistor having an input impedance which equals the collector impedance of the first transistor. The input circuit of a current mirror is included in the emitter circuit of the second emitter follower transistor and the output circuit is connected in parallel with the d.c. blocking impedance to keep the collector currents in the two emitter followers equal and constant.

The disclosed amplifier circuit includes a common base transistor, a turn-around device and a driver transistor, which is connected to a filter. An emitter follower stage is also connected to the filter. The turn-around device is connected between the common base and driver transistors. A diode connected transistor is utilized for compensating for the nonlinearity of the common base transistor. A first negative feedback path is provided between the driver and common base transistors to stabilize bias levels, increase amplifier output impedance and reduce distortion. A frequency compensation capacitor is connected to the driver transistor and a second negative feedback path is provided from the output of the emitter follower stage to the driver transistor. The second negative feedback path facilitates rapid discharge of the capacitor and driver transistor, a high slew rate and compensates for the nonlinearity of the emitter follower.

Sync-positive and sync-negative video signals appearing across load resistors of synchronous video detector employing array of NPN transistors are coupled via respective voltage dividers to complementary inputs of differential amplifier employing NPN transistors. Signals appearing across load resistor of amplifier are coupled via an active filter to video signal output terminal. Detector load circuits, amplifier load circuit, and active filter each provide high frequency roll off with break point lying between desired video passband and second subharmonic of picture carrier intermediate frequency. Active filter provides response boost within high end of video passband, and response null in vicinity of picture carrier intermediate frequency. Level shift circuit utilizes series resistance of active filter. Differential amplifier has current source responsive to amplifier output to avoid cut off of amplifier transistor receiving sync-negative drive.

In an amplifier device of the type comprising a differential amplifier including a pair of parallel-connected field effect transistors, an emitter grounded transistor responsive to the output of the differential amplifier and acting as class "A" amplifier, an output terminal connected to the collector electrode of the emitter grounded transistor and a constant current drive circuit connected to the commonly connected source electrodes of the field effect transistors, a feedback resistor is connected between the output terminal and the constant current drive circuit for modulating the current of the constant current drive circuit in accordance with the amplitude of the output signal.

An amplifier configuration is disclosed which utilizes a resistive, positive feedback network to develop a high input impedance. The amplifier, which is suitable for manufacture in monolithic integrated circuit form, includes a pair of differential transistors which are coupled to a current supply that provides a current having a predetermined temperature coefficient. A resistor, which is connected between the emitters of the differential transistors, develops either a temperature stable offset voltage or an offset voltage having a desired temperature coefficient in response to the current. A negative feedback circuit facilitates control of the bias voltages for the pair of differential transistors. Temperature stable quiescent input and output voltage levels are derived from the offset voltage through the feedback network.