Complementary to BC115

I guess I suspect that no-one manufactured a PNP version of the BC115.

In a non Hi Fi application, (modulator amplifier service for transmitter, not Hi Fi) which is the case here, can anyone please suggest what would be reasonable PNP replacement for BC115? Circuit works off 12V.

In fact, the circuit is here, where I might want to change 15VT1:

http://homepage.ntlworld.com/richards_internet/TEMPORARY/circuit.html
 
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I'm a right stickler for drawing circuits that make it easy. I always "want" to see emitters of transistors that are in a Common Emitter arrangement, on the same side as, or pointing to ground!

I should really stick with the BC115, just show emitter towards ground.

15VT1 on the original circuit just bugs me with it's emitter pointing up the schematic!

(BTW, I am on pills for this condition).
 
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Ian Finch

Member
Paid Member
2010-04-11 4:22 am
Coffs Harbour, NSW
Yes, nothing of BC115 is particular except no complement, only low gain, low dissipation and Ft 80mHz.

As an audio driver, you might look to more modern high voltage types (BC546/56 as listed by Wahab or 2n5401/5551 etc.) in an effort to limit Hfe to original part spec, if there is a stability issue in your application.

Something non-RF guys often neglect is the sensitivity of audio circuits to RF. High gain/Ft audio parts where they are not strictly needed can cause mayhem and QRP transmitters, for example, are notorious for such problems where RF and AF circuits are in close proximity and poorly shielded IME.
 
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The circuit you are looking at is for Germanium transistors, which is why most of them are PNP and the powersupply is -24V with respect to ground. This was typical of Ge-based transistor circuits. Similarly the transformer coupling is a sign of Valve type design, with Ge transistors substituted.

What does the circuit actually do? It looks like some kind of microphone amplifier.
 
The circuit you are looking at is for Germanium transistors, which is why most of them are PNP and the powersupply is -24V with respect to ground. This was typical of Ge-based transistor circuits. Similarly the transformer coupling is a sign of Valve type design, with Ge transistors substituted.

What does the circuit actually do? It looks like some kind of microphone amplifier.

It's a modulator. Well, an audio amplifier, that is used to modulate an RF carrier.

Audio quality will be naff by comparison to Hi Fi, but satisfactory for voice communications.