BJT Common Emitter - Hybrid-π Analysis

655

14:15:50

This is a quick hybrid-pi analysis of a common-emitter amplifier, values as given except early voltage = 200V and thermal voltage = 25mV@300k.
Re = Vt / IC = 25mV / 1mA = 25 Ohm
gm = 1 / (Re + RE) = 1 / (25 + 3000) = 330uS
RIn = hfe  / gm = 100 / 330uS = 303kOhm
Rout = VA / IC = 200V / 1mA = 200kOhm
Av = -gm * RC = -330uS * 5000 = -1.65
Zin (bias network) = ~40kOhm

published 11 years ago

rbrtkurtz

11 years ago

Wouldn't Zin be closer to 30kOhm? Anyhow, this looks like it would be a good example to use for a more detailed analysis of how the amplifier works. Kudos.

Chryseus

11 years ago

Yep 32k to be precise, I'm writing a more detailed article on using hybrid-pi for my blog, www.electrical-workbench.co.uk

rbrtkurtz

11 years ago

Cool!

rbrtkurtz

11 years ago

Wait. Are you http://www.imdb.com/name/nm0000249/ ?

Chryseus

11 years ago

@rbrtkurtz heh, nope.

hurz

11 years ago

Input Z is about 303k || 47k || 100k which is ~29kOhm. Heuristic proof is 17.3uA input current at 500mV is ~29kOhm measured. However good example!

moaazroushdy

10 years ago

Nice work

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