A P P L I C A T I O N S - Kenwood VT-171 Instruction Manual

6. A P P L I C A T I O N S

The basic use of your V T - 1 7 1 ["VT-171EJ is to measure
sinusoidal wave voltages a s an A C v o l t m e t e r . In addition,
it provides a wide v a r i e t y of applications as described
below.
(1) Amplifier Gain Measurement
Y o u r V T - 1 7 1 [ " V T - 1 7 1 E J is capable of measuring an
a m p l i f i e r g a i n , which is a signal magnification f r o m
point A to B in Figure5 w i t h a signal generator
connected to the a m p l i f i e r input.
signal levels at points A and B are a and b d B ,
respectively, then the gain is ( b - a ) d B .
A l s o , the method is applicable to negative-feedback
a m p l i f i e r s ; t h a t i s , it is a v a i l a b l e for measuring a n
open loop gain of each a m p l i f i e r circuit w i t h the
negative-feedback signal leaves applied.
F u r t h e r , the method can be used for measuring the
frequency responses of given c i r c u i t s by changing the
signal generator frequency.
A s an example, let us calculate the open loop gain
( f r o m point A to B ) of the negative-feedback a m p l i f i e r
shown in F i g u r e 6 . Assume t h a t the measured level a t
®
If the measured
point A b e + 1 . 5 d B in the - 6 0 d B range and that of
point B - 4 d B in the +10dB range. The gain f r o m point
A to B is
( + l 0 d B - 4 d B ) - ( - 6 0 d B + 1.5dB) = 64.5dB.
S I G N A L
G E N E R A T O R
Figure 5 - Amplifier Gain Measurement.
SIGNAL
G E N E R A T O R
Figure 6 - Negatve Feedback Amplifier Gain Measurement.