Hi there everybody, I'm doing a course on electronics and I've been landed with an assignment I'm really stumped by. I've put quite a lot of time into trying to understand this but as I'm working off dribs and drabs from my college tutor along with some vague web tutorials I'm kind of at a loose end.
I'll post what I've got so far along with a schematic
The task is to design and built a common emitter class A amplifier using the
BJT Q2N2222 transistor and the following specifications:
Vcc = 18v
Lower cut-off frequency must be 210 Hz
Upper cut-off frequency must be 500 kHz
Gain β = 95
Rout = 17kΩ
Vin = 7mVrms
The collector current at operating point Icq is 10mA
I've tried the following calculations but the results indicate they seem to have gone quite badly wrong. .
Vce = 0.5 x Vcc = 9V
Ic = Vcc - Vce / Rout
= 18-9 / 17000
=5.29 e-4 A
I've been told to use Ve = 3V, I really have no idea why, I'd like to know where this comes from
Vout = Gv x Vin
= 95 x 7e-3
=0.665Vrms
=0.940 Vpeak
Total voltage swing = 0.94 x 2 = 1.88V peak to peak
Rc = Vcc - Ve - Vce / Ic
= (18 - 3 - 9) / 10e-3
=600Ω
Re = Vce / Ic
= 3 / (10e-3)
=300Ω
Next I need to calculate IBq, I've been told that you should use the maximum gain for the transistor being used, 180, giving the equation;
IBq = 10e-3/180 = 5.56e-5
Unfortunately this is where it all goes pear shaped and my R1 and R2 values are a bit crazy.
Below are screenshots of what I simulated, even if they are way, way off I'll just put them here anyway
http://yfrog.com/jascreenshotczj
http://yfrog.com/j0schematicj
Sorry about the long post, any help with this would be very greatly appreciated
Thanks guys
I'll post what I've got so far along with a schematic
The task is to design and built a common emitter class A amplifier using the
BJT Q2N2222 transistor and the following specifications:
Vcc = 18v
Lower cut-off frequency must be 210 Hz
Upper cut-off frequency must be 500 kHz
Gain β = 95
Rout = 17kΩ
Vin = 7mVrms
The collector current at operating point Icq is 10mA
I've tried the following calculations but the results indicate they seem to have gone quite badly wrong. .
Vce = 0.5 x Vcc = 9V
Ic = Vcc - Vce / Rout
= 18-9 / 17000
=5.29 e-4 A
I've been told to use Ve = 3V, I really have no idea why, I'd like to know where this comes from
Vout = Gv x Vin
= 95 x 7e-3
=0.665Vrms
=0.940 Vpeak
Total voltage swing = 0.94 x 2 = 1.88V peak to peak
Rc = Vcc - Ve - Vce / Ic
= (18 - 3 - 9) / 10e-3
=600Ω
Re = Vce / Ic
= 3 / (10e-3)
=300Ω
Next I need to calculate IBq, I've been told that you should use the maximum gain for the transistor being used, 180, giving the equation;
IBq = 10e-3/180 = 5.56e-5
Unfortunately this is where it all goes pear shaped and my R1 and R2 values are a bit crazy.
Below are screenshots of what I simulated, even if they are way, way off I'll just put them here anyway
http://yfrog.com/j0schematicj
Sorry about the long post, any help with this would be very greatly appreciated
Thanks guys
Last edited: