5.2.
TEMPERATURE SENSITIVE OSCILLATOR
Figure 5-2: TEMPERATURE SENSITIVE OSCILLATOR
Temperature changes are sensed by the thermistor RT1/RT2 connected with Rl across the 1:2
ratio autotransformer T101. As the temperature decreases, the thermistor resistance increases
and the voltage divider output to the base of Q101 increases. As soon as this voltage exceeds
half the transformer output, the circuit gain becomes greater than one and oscillation occurs.
5.3.
AMPLIFIER AND DETECTOR
Figure 5-3: AMPLIFIER AND DETECTOR
The output of the oscillator is amplified by Q103 and rectified by a voltage doubler, consisting of
C105, CR103, CR104 and C107. The resistor R115 gives current limiting protection for the next
stage.
T101
Q101
P1-12
P1-9
P1-10
C104
R110
R1
RT1/RT2
t
P2-C
P2-D
P2-A
Q102
