5088 transistors

[estch71]

kind of a silly question but, I'm building a Green Ringer and do not have any 5088's.  I do, however, have some BS170's, 2n2907a's, and a slew of 4403's.  Which one would be best to swap out for the 5088?  I realize that the 5088 has more gain to it but, I'm willing to sacrifice a little gain.

Thanks!

[Mark Hammer]

Gain is not really the issue, but transistor type IS. 

The BS170 is a MosFet, and the 4403 is a PNP.  Depending on the build diagram you follow, the circuit requires either one PNP and two NPNs, or two PNPs and one NPN.  You cannot substitute the one type for the other.  The 4403 is a decent replacement for the PNP (2SA666 or 2N3906), but a 5088 is an NPN type and you don't appear tohave anything to sub for it, or at least haven't listed any.

[estch71]

Gotcha.  I have some 4401's as well.

[Mark Hammer]

Well those would work just fine as a sub for the NPN.

[R O Tiree]

BS170 is a N-Channel Enhancement MOSFET, so not suitable at all for replacing a bog-standard NPN BJT (bi-polar junction transistor)

2N2907 has a relatively low hfe figure (100-300) compared with the 2N5088 (300-900 or so). That said, the first stage of the green ringer only has a gain of about 3 so well inside the capabilities of both transistors. Stage 2 is just a unity-gain phase-splitter and stage 3 is a unity-gain emitter follower. This is not a high-gain circuit, so this one should be just fine for Q1 and Q3.

2N4403 is a PNP BJT, so not suitable as a substitute for a 2N5088, but it would be just dandy for Q2 in the Green Ringer circuit.

Hope it works OK.

Edit: Mark beat me to it, as 'er indoors put my tea on the table just before I was about to post this and I only just came back to it. There's extra info in here, so I'll leave it as is.

[Mark Hammer]

Hearing it two ways only serves to make it more persuasive.

(I'm only fast today because it is a VERY slow day at work)

[estch71]

I tried the 4001's which didn't seem to work, although I think there was something wrong in the construction of the board itself.  Going to try again today.  Thanks so much for the advice!

[Mark Hammer]

Be careful about the pinouts.  They're not all the same.