Some folks wishing to go beyond mods to existing designs, might find these discrete transistor design articles of interest.
http://www.experimentalistsanonymous.com/ve3wwg/doku.php?id=ss_circuit_engineering&#design_articlesThere you will find design articles for:
- Designing an Emitter Follower Stage (start here)
- Designing an Common Emitter Stage
- Designing a Phase Splitter
- Grounded Emitter Design with Feedback
So often today (myself included), we just reach for an opamp for nearly everything (audio). Yet, very often a simple little discrete transistor stage or two can be used instead. The main reason for this is the simple fact that opamps are easier to design for.
I've worked with tubes in the past a fair bit and found them easy to design for (for audio). But transistors were not so simple. So it has been on my to-do list to overcome this for quite some time.
Over the last several months I have been hitting the books and simulating circuits in LTspice to check my understanding and perform experiments (much easier than using actual hardware). Along the way I have also enlisted some help from newsgroup sci.electronics.design on a couple of occasions (the grounded emitter stage with feedback presented some special challenges).
So this effort has in part been to document what I've learned. But since it is a shared resource, I am hoping others can benefit from my own hard won lessons. Available textbooks very often are focused on
how things work and how formulas were derived. Most of us are just willing to be told what the formulas are
. The challenge a designer faces is to know how to
choose the necessary component values. This procedure is not usually well covered.
So what I have focused on in these articles is how to
design the circuit. I step you through a process of computing and selecting values.
A solid grasp of ohms law will be required (ohms law is used a lot, 2nd perhaps only to Murphey's law). Additionally a rudimentary understanding of impedance and transistor operation will be helpful. In these articles impedance is simple resistance, so things don't get that complex (pun intended).
From these articles, you should be able to look at an existing design and compute:
- stage gain
- input impedance
- output impedance
If you spot any errors or suspected errors, please freely point them out and I'll check or correct them.
This has been a fun ride so far. It's like learning to ride a bicycle. Once you know how to ride, there are so many more places you can go!
Don't be afraid to acquire some good used textbooks. Knowledge is power. Buying used means you can buy them at hobby prices. You'll also not be afraid to make notes in your $3 + shipping textbook. Books are your ticket to empowerment.
