Programmable amplifier for electronic probe

摘要

The amplifier includes an input transistor emitter (106) and an output transistor emitter (108) connected together to form an emitter pair. A current source (125) is connected to the emitter pair via a transistor which is controlled by a latch. Programming the latch permits the channel to be turned on or off. The emitter pair is connected to a positive voltage through a resistor (144) and to ground through a diode (142) to force it to a controlled off voltage which prevents signals from passing when the channel is off. There is an output driver amplifier (118) in a feedback circuit. An out-disable circuit controls the voltage and current of the output driver amplifier to place the output in a state in which it appears electrically as an open circuit when the channel is off.