Figure 12.

Feedback Differential Amplifier.

and the RANGE switch to change metering loop gain so that the meter will read

full scale for each power range.

Potentiometer adjustments are provided to

accurately set the calibration on each range. Diode A1CR6 provides temperature

compensation for A1Q10.

n. Meter Circuit.

A simplified schematic diagram of the meter circuit is shown in Figure

14.

The meter circuit includes feedback current-squared generator A1Q11, a

squaring circuit, the meter, RECORDER/LEVELER and DVM jacks, J2 and J4.

The

purpose of the meter circuit is to convert a linear voltage function,

proportional to the square root of applied power, to a square function so that

power may be indicated on a linear meter scale. The linear voltage function is

applied to the base of A1Q11 and is converted to a square law function by the

squaring circuit in series with A1Q11 emitter.

o. Metering Circuit Differential Amplifier.

(1) The metering circuit RECORDER/LEVELER output is a voltage of low

source impedance necessary for isolation between a recorder or leveler

amplifier and the metering circuit of the power meter. The isolation circuit

comprises the differential amplifier A2Q6-A2Q7 and output transistor A2Q8. The

voltage developed across A2R38 for the DVM output is referenced at the base of

A2Q6 for comparison to the voltage at the RECORDER/LEVELER jack placed on the

base of A2Q7. Any difference voltage creates an error voltage that changes the

base-emitter bias on

Integrated Publishing, Inc. |