# Tuned voltage amplifier

#### scarlet

Joined Dec 20, 2008
4
hello everyone
can anyone answer any these questions?
1.what are the effects of the reactance ,capacitance, impedance in the Tuned voltage amplifier?
2.what is the importance of center frequency and bandwidth of a Tuned voltage amplifier used in a radio receiver?
3.what is the selectivity of a Tuned voltage amplifier?
4.what is the Q factor of a Tuned voltage amplifier, and who can i find it or calculate it?

answering any of them would be fine, and thanks either way

#### beenthere

Joined Apr 20, 2004
15,808
It might be that you need a text that deals with intermediate frequency (IF) amplifiers.

#### Robert Hall

Joined Dec 22, 2008
1
What text are you working from?

Basic Electronics and Linear Circuits (N. N. Bhargava, S. C. Gupta, D. C. Kulshreshtha) has this as chapter 11

Starting on page 369 it gives the answers pretty much right down the line.

These are pretty easy to answer however,

1. has to do with the efficiency of the amplifier, if you are trying to amplify a higher frequency ( > 1MHZ) one starts dealing with resonance and power efficiency. In simple terms, if your amplifier is not tuned to the frequency you are amplifying you get power feedback which can destroy your amp.

2. Center frequency and bandwidth is about amplifying only the frequency you want to amplify. If you have, for example, harmonics off the main frequency you may not want to amplify them, only the frequency you are interested in. Think of out of band amplification (amplification of frequencies you don't want to amplify) as noise or distortion of the main signal.

3. Selectivity means how well can I amplify only the signal I want, not things I don't want to amplify such as harmonics.

4. You can find the q by knowing the reactance, we can call it X sub L (or C) and the result would be Q = X/R and X = w (omega or frequency) / R or omega = 2 pi frequency so you can write it Q = 2 pi Freq L/R.

Kind of hard to write equations in this editor. the whole point to this is that if your amplifier is at resonance you can reduce your calculations to Ohms law.

Does that help?