I was given an outside assignment this week in my communications class to build an RF amplifier for use with an AM transmitter lab the rest of the class is building. I had already finished my transmitter and hooked a microphone to it to test, but we were only able to get a very weak signal at best. I was told to use what parts I have in my parts kit to build a quick and dirty amplifier. I have basic transistor knowledge, but have not designed too many circuits yet.
I've done a few hours worth of reading between my text book and google searches, and have come up with a very rough idea of where to start. I'm just going to use this simple circuit that I've seen in a few locations including wikipedia (I know, I know; don't use wikipedia). It's very close to the design i had in mind with the addition of Q3.
For Q1, Q2 and Q4 I'm going to use 2n3904 and will use 2N3906 for Q5 and Q3. D1 and D2 will be 1n4148. The input comes from a XR2206 IC with a 2vpp 1600kHz signal. A supply of 20V will be used.
I understand the operation of the differential amplifier of Q1 and Q2, but have not calculated the necessary values for the biasing resistors. How to calculate R7 and R8 is eluding me. Also, how do you figure R6? I guess it would help if i fully understood the operation of Q3.
Any help in learning how to design this would be much appreciated. I will update with more information as I crunch numbers.
I've done a few hours worth of reading between my text book and google searches, and have come up with a very rough idea of where to start. I'm just going to use this simple circuit that I've seen in a few locations including wikipedia (I know, I know; don't use wikipedia). It's very close to the design i had in mind with the addition of Q3.
For Q1, Q2 and Q4 I'm going to use 2n3904 and will use 2N3906 for Q5 and Q3. D1 and D2 will be 1n4148. The input comes from a XR2206 IC with a 2vpp 1600kHz signal. A supply of 20V will be used.
I understand the operation of the differential amplifier of Q1 and Q2, but have not calculated the necessary values for the biasing resistors. How to calculate R7 and R8 is eluding me. Also, how do you figure R6? I guess it would help if i fully understood the operation of Q3.
Any help in learning how to design this would be much appreciated. I will update with more information as I crunch numbers.
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