| 摘要 |
A differential amplifier having a pair of common base transistors with emitter electrodes adapted for coupling to an input signal and collector electrodes coupled to a voltage source through a pair of resistors. A pair of clamping diodes is connected, in opposing polarity, across the collector electrodes to limit the differential voltages produced at such collector electrodes. A bias circuit is provided between the voltage source and the common base electrodes of the transistors to provide a bias voltage at the common base electrodes which is as close to the voltage of the voltage supply without biasing either one of such pair of transistors into saturation. The bias circuit includes a first resistor connected between the voltage source and the common base electrodes and, in parallel with such first resistor, second resistor and serially connected diode. The emitter electrodes of the pair of transistors is connected to a current source matched to a current source coupled to the bias circuit so that the voltage drop produced across the bias circuit is equal to the voltage drop produced between the voltage source and the collector electrodes of the pair of transistors. With such arrangement, such differential amplifiers may be used in a cascade connected multi-gain stage of a comparator circuit with level shifting provided therein with Zener connected transistors following the cascaded gain stages thereby reducing the effect of process created variations in the Zener connected transistors and the pair of clamping diodes on such comparator circuit.
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