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How to compute base biasing resistor for class C amplifier

Started by amal banerjee October 31, 2019
Could some electronics guru here please tell me how to
compute the base biasing resistor for class C amplifier. 
From the Vce-Ice- load line graph, the Q point has to 
be below the horizomtal axis, i.e., Vce < 0.0. All hints,
suggestions are welcome. Thanks in advance.
 
 amal banerjee wrote:

----------------------
> > Could some electronics guru here please tell me how to > compute the base biasing resistor for class C amplifier. > From the Vce-Ice- load line graph, the Q point has to > be below the horizomtal axis, i.e., Vce < 0.0. All hints, > suggestions are welcome. Thanks in advance.
** Mosfet or BJT? Your is another PITA information free post. Or is that an exam question ?? ..... Phil
On Wed, 30 Oct 2019 21:52:19 -0700, amal banerjee wrote:

> Could some electronics guru here please tell me how to compute the base > biasing resistor for class C amplifier. From the Vce-Ice- load line > graph, the Q point has to be below the horizomtal axis, i.e., Vce < 0.0. > All hints, > suggestions are welcome. Thanks in advance.
All the questions you've been posting could be answered by getting a copy of this book: https://www.ebay.co.uk/itm/RF-Circuit-Design-by-Christopher-Chris-Bowick- very-good-looked-after-condition/303221019625? hash=item46996193e9:g:Oc0AAOSw9M9dJ2YD And you get can even more value out of it by spotting all the errors! :) Still very instructional, though, seriously. -- This message may be freely reproduced without limit or charge only via the Usenet protocol. Reproduction in whole or part through other protocols, whether for profit or not, is conditional upon a charge of GBP10.00 per reproduction. Publication in this manner via non-Usenet protocols constitutes acceptance of this condition.
On Wednesday, October 30, 2019 at 9:52:23 PM UTC-7, amal banerjee wrote:
> Could some electronics guru here please tell me how to > compute the base biasing resistor for class C amplifier. > From the Vce-Ice- load line graph, the Q point has to > be below the horizomtal axis, i.e., Vce < 0.0. All hints, > suggestions are welcome. Thanks in advance.
Just buy Steve Cripps' book and be done with it. RF Power Amplifiers for Wireless Communications
>** Mosfet or BJT?
Your bad this time dude, he said BASE biasing.
On Wednesday, October 30, 2019 at 11:52:23 PM UTC-5, amal banerjee wrote:
> Could some electronics guru here please tell me how to > compute the base biasing resistor for class C amplifier. > From the Vce-Ice- load line graph, the Q point has to > be below the horizomtal axis, i.e., Vce < 0.0. All hints, > suggestions are welcome. Thanks in advance.
In class C the base bias will be reverse. How much reverse determines the duty cycle. That determines most of the rest. You are basically pulsing a tuned circuit, there is not much other reason to use class C. It is the most efficient but there are many things it cannot do.
On Friday, November 1, 2019 at 11:19:40 AM UTC-4, Cursitor Doom wrote:
> On Wed, 30 Oct 2019 21:52:19 -0700, amal banerjee wrote: > > > Could some electronics guru here please tell me how to compute the base > > biasing resistor for class C amplifier. From the Vce-Ice- load line > > graph, the Q point has to be below the horizomtal axis, i.e., Vce < 0.0. > > All hints, > > suggestions are welcome. Thanks in advance. > > All the questions you've been posting could be answered by getting a copy > of this book: > > https://www.ebay.co.uk/itm/RF-Circuit-Design-by-Christopher-Chris-Bowick- > very-good-looked-after-condition/303221019625? > hash=item46996193e9:g:Oc0AAOSw9M9dJ2YD > > And you get can even more value out of it by spotting all the errors! :) > > Still very instructional, though, seriously. > > > > -- > This message may be freely reproduced without limit or charge only via > the Usenet protocol. Reproduction in whole or part through other > protocols, whether for profit or not, is conditional upon a charge of > GBP10.00 per reproduction. Publication in this manner via non-Usenet > protocols constitutes acceptance of this condition.
There is a copy of Bowick's book in our office library. Unfortunately, his class C amplifier circuit diagram is peculiar. It works only on LTSpice, not HSpice or Ngspice.
On Friday, November 1, 2019 at 5:07:19 PM UTC-4, Simon S Aysdie wrote:
> On Wednesday, October 30, 2019 at 9:52:23 PM UTC-7, amal banerjee wrote: > > Could some electronics guru here please tell me how to > > compute the base biasing resistor for class C amplifier. > > From the Vce-Ice- load line graph, the Q point has to > > be below the horizomtal axis, i.e., Vce < 0.0. All hints, > > suggestions are welcome. Thanks in advance. > > Just buy Steve Cripps' book and be done with it. > > RF Power Amplifiers for Wireless Communications
I have PDF copy of his book that I downloaded a few years ago. But like a number of other authors, it suffers from too mucj text the design examples are bare bones and the reader has to a lot of calculations himself to determine the sequence of calculation steps used to arrive at an answer.
On Saturday, November 2, 2019 at 8:40:51 AM UTC-4, jurb...@gmail.com wrote:
> On Wednesday, October 30, 2019 at 11:52:23 PM UTC-5, amal banerjee wrote: > > Could some electronics guru here please tell me how to > > compute the base biasing resistor for class C amplifier. > > From the Vce-Ice- load line graph, the Q point has to > > be below the horizomtal axis, i.e., Vce < 0.0. All hints, > > suggestions are welcome. Thanks in advance. > > In class C the base bias will be reverse. How much reverse determines the duty cycle. That determines most of the rest. You are basically pulsing a tuned circuit, there is not much other reason to use class C. It is the most efficient but there are many things it cannot do.
Thank you very much for the clarification.
Fuck all that. Hook up your circuit with a bipolar and couple capacitively to the base but with like a 20 meg pot to ground. 

When you find your operating point just shut it down, take an ohmmeter to the pot where you set is an use that value. 

Yeah, that is cowboy engineering but it works.