Amplifier

TM 11-6625-646-15

first

and

corresponding

components

perform

capacitor C604. Capacitor C610 bypasses the signal

corresponding functions.

around emitter resistor R632. Negative feedback for

stability is provided through resistor R628.

d. Operating voltage (approximately 23 volts dc) is

c. Except for reference designations and the

connected to the emitter of amplifier Q606 through

resistor R651 and ac degeneration resistor R650; base

values of certain components which alter its gain, the

bias is furnished by resistor R649. The sine wave

second amplifier stage is identical with the first stage.

output of the second amplifier is connected through dc-

Corresponding components perform corresponding

blocking capacitor C614 to the base of transistor Q606.

functions.

The amplified output signal is developed across the

d. The square wave output of the two-stage

primary winding of transformer T604, phase corrected

amplifier is coupled through dc-blocking capacitor C603

by capacitor C619 and coupled through dc-blocking

to an integrating network consisting of resistors R626,

capacitor C618 to the meter rectifier stage and through

R629, and R634 and capacitors C606, C607, and C608.

pin 25 of the card connector and the test set receptacle

In the integrating network, the square wave is

to the feedback (cancellation voltage) circuit of the SAS

converted, first to a triangular wave, then to a sine

amplifier. Capacitor C620 bypasses the signal around

wave.

emitter resistor R651. Resistor R650 provides negative

feedback in the third stage and resistor R636 completes

the external feedback loop to the first stage, establishing

1-24. Amplifier

gain and phase shift.

(fig. 1-2)

In the three-stage amplifier as it is used in the SAS

bench test set the sine wave (approximate) signal from

1-25. Axis Meter Rectifier

the integrating network is amplified and coupled as a

(fig. 1-2)

simulated link feedback (cancellation) signal to the SAS

In the meter rectifier (phase-sensitive demodulator)

amplifier channel and to the simulator card meter

stage, the simulated extensible-link feedback signal

rectifier stage. Amplifier stability is provided by one

from the amplifier is converted to a positive or negative

external and three internal feedback loops and the total

dc voltage. The polarity of this voltage is a function of

gain of the 3-stage amplifier is approximately 1000.

the phase of the ac input signal. This stage functions as

a. B + (27 volts dc from the dc supply of the test

a meter rectifier when relay K601 is released (AXES

set) is connected to the amplifier through decoupling

METER READ switch S4 at CLOSED LOOP

networks consisting of resistor R653 and capacitor C617

FEEDBACK V). When relay K601 is operated (AXES

and resistor R647 and capacitor C616. Operating

METER switch S4 at OPEN LOOP TOR MOT V), the

voltage (approximately 23 volts dc) is connected to the

meter rectifier is inoperative and the open loop output of

emitter of first amplifier Q604 through resistor R639;

the SAS amplifier channel is connected through

base bias is furnished by resistor R638.

contacts 5 and 2 and through meter multiplier R640 and

contacts 1 and 6 of relay K601 to the AXIS meter.

b. The sine wave input signal is connected through

gain control resistor R635 and dc-blocking capacitor

NOTE

C611 to the base of PNP transistor Q604.

The

The dc output of the meter rectifier

amplified output signal is developed across collector

stage is taken across the center taps

load resistor R641 and coupled to the second amplifier

of reference voltage transformer

stage through dc-blocking capacitor C612. Capacitor

T603 and signal transformer T602

C613 bypasses the signal around emitter resistor R639

and applied to the zero-center axis

and resistor R637 provides negative feedback for

meter. To maintain consistency in

stability.

the direction of meter indications

c. Except for the reference designations of its

components, the second amplifier is identical with the