Bitx20 mic amp on LTSpice; common emmiter analysis has begun


LTSpice simulation of the Farhan Bitx20 mic amp (using assumed 80mV peak-to-peak signal from Radio Shack microphone)

Lots of fun with Spice!  I don’t know why I stopped using this valuable, fun and easy to use tool after I got through college years ago.  I remember suffering with the predecessor “PSPICE” tool where you had to code everything in via text commands!  Painful.  This GUI stuff is a breeze and a load of fun.  I think it only took me 15 minutes to throw this together.

I kind of screwed up with the 80mV peak-to-peak mic output!  That would only happen if I was really yelling into this mic.  But I’d already done the screen snapshot with it and it’s fine for my learning purpose.

With the 80mV peak to peak, the output waveform (ignoring the DC offset) is about 700mV peak to peak.  Almost 10x the input voltage.

I want to do some homework to understand this circuit a little better.  First I know I can calculate the DC bias parameters fairly easily.  But knowing the decision behind the choice of capacitors and the desired gain of this circuit would be nice.  Maybe I learned this once but I am more than rusty at this point.  I’ve got plenty of resources at my disposal, including several textbooks and probably the bitx20 group as well as feedback from this blog.  Just time to dive in.

demassa amp analysis

Excerpt from “Electrical and Electronic Devices, Circuits and Instruments” text by DeMassa,1989.

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1 Response to Bitx20 mic amp on LTSpice; common emmiter analysis has begun

  1. Pingback: BITX related on-line websites, facebook pages, and blog sites – uBitx

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