One transistor class A amplifier

374

08:14:00

This is a very simple amplifier based on an npn transistor for weak signals. It could be used in audio or other branches of electronics. On YouTube I have a video where I explain (Spanish) how to calculate this circuit in its static and dynamic form. You can use YT machine translator, content is mathematical. https://youtu.be/cMysKkmdw4c

published 6 years ago

crake

6 years ago

Too much gain but looks good otherwise

hurz

6 years ago

Yes, too much gain which does cause high distortion THD. This can be allready noticed by the asymetric Vpp output +783mV to -950mV. This is because you are riding with 10mV directly on the Vbe characteristics of an diode. From input over 10uF to base and from emitter directly over 22uF back to input. No impedance in between input and base emitter diode. Riding on a diode above 2mV up and down cause horrible distortion. What you need is some extra resistance at input or even better at emitter an extra 200Ω in series to 1k and 22uF. The input network is BTW also for a BJT to optimistic high resistive. 100k 33k will fit better. The mega ohm tesistor lets a low beta BJT suffer from pulling even 10kOhm. The maximum hFe or Beta you will get for little standard BJTs more around Ice 10mA !

hurz

6 years ago

here an xample for 20dB or factor 10 gain which is a good thumb of rule to get a njce symetric peak to peak output voltage and a low THD. http://everycircuit.com/circuit/4733012187807744

add comment in editor

EveryCircuit is an easy to use, highly interactive circuit simulator and schematic capture tool. Real-time circuit simulation, interactivity, and dynamic visualization make it a must have application for professionals and academia. EveryCircuit user community has collaboratively created the largest searchable library of circuit designs. EveryCircuit app runs online in popular browsers and on mobile phones and tablets, enabling you to capture design ideas and learn electronics on the go.