davenn
Moderator
hi guys,
will be the first to admit that my transistor theory is a bit weak at times....
have been sorting out a piece of circuitry for another guy and I cant quite explain the circuit operation of 2 of the transistors.....
The circuit for for power control of an RF amplifier, a detected and rectified voltage comes down to the base of Q211 from a reflected power sensor. and via Q211,212 and 213 the corrent to the base of Q1 is controlled. This controls the voltage/current from the emitter of Q1 up to the final output power transistor (not shown).
Under normal conditions, where there is little or no reflected power, Q211 isnt conducting Q212 is conducting via the current flowing from the 8V TX rail via R230 and 231 to its base. Q213 is fully conducting allowing Q1 to fully conduct and supply full voltage to the final transistor.
What I cant fully explain is the interaction of Q212 and 213.
when Q 212 is conducting so is Q213 and visa versa .... but how is Q212 turning Q213 on and off ?
Dave
will be the first to admit that my transistor theory is a bit weak at times....
have been sorting out a piece of circuitry for another guy and I cant quite explain the circuit operation of 2 of the transistors.....
The circuit for for power control of an RF amplifier, a detected and rectified voltage comes down to the base of Q211 from a reflected power sensor. and via Q211,212 and 213 the corrent to the base of Q1 is controlled. This controls the voltage/current from the emitter of Q1 up to the final output power transistor (not shown).
Under normal conditions, where there is little or no reflected power, Q211 isnt conducting Q212 is conducting via the current flowing from the 8V TX rail via R230 and 231 to its base. Q213 is fully conducting allowing Q1 to fully conduct and supply full voltage to the final transistor.
What I cant fully explain is the interaction of Q212 and 213.
when Q 212 is conducting so is Q213 and visa versa .... but how is Q212 turning Q213 on and off ?
Dave