CASCODE AMPLIFIER
This is a form of composite transistor where CE and CB have been cascaded. By using the composite form we achieve best of both the circuit configurations namely we get a moderate input impedance and high voltage gain of CE configuration and almost near unilaterality , very large output impedance , large output voltage swing limited by BVCBO and much larger Band Width of CB configuration. Because of near uni-laterality on account of near zero reverse transmission factor, this CASCODE is very suitable RF Amplifier applications. This configuration is also suitable for constant current drive as required in generating SAW TOOTH WAVEFORM.
C1 provides the ground to Q2 under signal condition.
C2 is the coupling capacitor and C3 provides the by-pass capacitor of emitter resistance.
INCREMENTAL MODEL
Overall Reverse transmission factor= hre.hrb
JFET-Bipolar Cascode
The following schematic shows the JFET-Bipolar Cascode Circuit Diagram. The JFET-Bipolar cascode circuit will provide full video output for the CRT cathode drive. Gain is about 90.
The cascode is a two-stage amplifier composed of a transconductance amplifier followed by a current buffer. The cascode configuration eliminates Miller capacitance problems with the 2N4091 JFET, thus allowing direct drive from the video detector. An m derived filter using stray capacitance and a variable inductor prevents 4.5 MHz sound frequency from being amplified by the video amplifier.
Rooselvet Ramirez EES
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