Third Cascode Amplifier

Q132 and Q134, in conjunction with Q304 and Q308 in the Vertical Switching Circuit, form the Third Cascode Amplifier stage. Thermistor RT131 (between the emitters of Q132 and Q134) changes in value with changes in temperature. This varies the gain of the Third Cascode Amplifier stage to compensate for changes in total amplifier gain that occur with variations in operating temperature. The push-pull signals picked off in the emitters of Q132 and Q134 are converted to a single-ended signal by Q142 and Q148. This signal is amplified by common-base amplifier stage Q152 and applied to the bases of emitter followers Q162 and Q164. Q164 provides the output signal to the CH 1 VERT SIGNAL OUT connector located on the instrument rear panel. The output signal at the emitter of Q162 is used as the trigger signal source in the CH 1 positions of the Trigger SOURCE switches and as the signal source for emitter follower Q168. Q168 provides the X-axis signal from the Channel 1 Preamplifier to the Horizontal Amplifier in the X-Y mode of operation. CR164, CR165, CR166, and CR167 protect the emitter circuit of 0164 in the event large voltage levels are accidentally connected to the CH 1 VERT SIGNAL OUT connector. R155 adjusts the DC level of the CH 1 trigger source signal.

0 0

Post a comment