Q OUT

Figure 1. Step Gain Amplifier, Simplified Schematic

Amplitude Calibration Attenuator @

Q2 is an emitter follower buffer driving a second pin diode attenuator, CR11 to CR14. The current through CR11 and CR12 is determined by the front-panel control A6R1, AMPTD CAL. The current through CR13 and CR14 is fixed by R27. This circuit provides for amplitude calibration of the instrument.

21.4 MHz Output @

Qll and Q12 form the output stage for the Last Converter. Qll is an emitter follower driving a common emitter amplifier Q12.

Temperature Compensation Voltage Source @

Ql provides a voltage to set the current in CR8 to CR10 and CR15 to CR17. This voltage varies with temperature, changing the gain of the two step-gain amplifiers to compensate for gain changes with temperature elsewhere in the Last Converter.

A6A3 3