Transistor

[sssaaa]

i didnt found  NTE123AP transistor in my city.
what transistor i will use in the place of this transistor.

thanks

[sssaaa]

Hi Audioguru

I m using ur FM transmitter you said it will not work on less then 5 volts.

it also worked on 2.5volts? why?

I m using transistor shaped voltage regulator IC like yours.

[audioguru]

I designed the biasing of the preamp transistor for a regulated 5V supply so it could have enough voltage gain.
With a higher voltage then it is saturated.
With only 2.5V then it is cutoff as my simulation shows:

[sssaaa]

sorry i forgot to mention that

I m using this preamp with your transmitter
http://www.uoguelph.ca/~antoon/circ/preamp.htm

and your transmitter is worked when my battery voltage goes down to 2.5 volts

It means its oscillator which is connected with voltage regulator IC, and rf amp transistor which is connected directly, will also work on 2.5 volts ?

[audioguru]

sorry i forgot to mention that

I m using this preamp with your transmitter
http://www.uoguelph.ca/~antoon/circ/preamp.htm

and your transmitter is worked when my battery voltage goes down to 2.5 volts

My transitter already has a preamp transistor. I showed a sim with it cutoff and not working with a supply voltage of only 2.5V.
My transmitter is very sensitive to sounds. Adding another preamp would overload its input.

I also simulated the "preamp" circuit you found and it saturates with nearly any supply voltage because it is not designed properly.

[sssaaa]

i have two questions to ask you

1,  Your transmitter`s  oscillator and rf amp works on 2.5 volts?

2,  what is the output of LM2931A on 2.5 volts?

thanks

[audioguru]

1,