Needing a little help. Yes, I am a student and this is a project. I am returning to school part-time after working for 20 years, so I am not looking for someone to do my work but I would like someone to tell me where I can look, or advise some rules of thumb I can use for the project below. This is Electrical Engineering which does not perfectly match my background but it is a topic I am interested in.
Our project is to build a 3 stage amplifier, PSpice and actual circuit. I have a model in PSpice that meets all of the design criteria but when I actually build the circuit it is losing the AC components. DC is close all the way through the circuit. I have a schematic I can upload tonight but I really am looking for direction on why it does not match actual circuits and how I can improve the design, hoping it is around bias values. Had a couple of design that were a little too complex for me solve (All MOSFET w/mirror and Darlington pair designs) so I have switch back to the simplest design I can thank of MOSFET, BJT, BJT. I have quite a bit of info on the design so if you feel you can help and need more info I do not mind sharing.
Criteria
Gain =50, Rin^200k, RL=50, distortion <-30dB
Design
3 stage
MOSFET and BJT
Stage 1
Biased MOSFET (no Rs)
PSpice gain .95, Actual gain .45
Stage 2
Biased BJT 2N2222 Common Emitter (no Rs)
PSpice gain 14 Actual 4
Stage 3
BJT 2N2222 Common Collector
PSpice gain 51 Actual .9
Possible problems I see:
Is current messing me up? Starting with 5VDC and 10mVPP signal
Everything look like it is the correct region, MOSFET=Saturation, BJT=Active, maybe I am wrong
Add Rs to stabilize circuit, temperature seems to have some impact
Are the PSpice components design correctly? Given to us by instructor but are they accurate enough?
Will balancing the BJT bias help?
MOSFET is 620k||500K in PSpice for the same DC values through the entire system I need 639k||300K. In PSpice the actual best seem to be a ratio of the PSpice numbers.
Thanks,
asdfrewq
Our project is to build a 3 stage amplifier, PSpice and actual circuit. I have a model in PSpice that meets all of the design criteria but when I actually build the circuit it is losing the AC components. DC is close all the way through the circuit. I have a schematic I can upload tonight but I really am looking for direction on why it does not match actual circuits and how I can improve the design, hoping it is around bias values. Had a couple of design that were a little too complex for me solve (All MOSFET w/mirror and Darlington pair designs) so I have switch back to the simplest design I can thank of MOSFET, BJT, BJT. I have quite a bit of info on the design so if you feel you can help and need more info I do not mind sharing.
Criteria
Gain =50, Rin^200k, RL=50, distortion <-30dB
Design
3 stage
MOSFET and BJT
Stage 1
Biased MOSFET (no Rs)
PSpice gain .95, Actual gain .45
Stage 2
Biased BJT 2N2222 Common Emitter (no Rs)
PSpice gain 14 Actual 4
Stage 3
BJT 2N2222 Common Collector
PSpice gain 51 Actual .9
Possible problems I see:
Is current messing me up? Starting with 5VDC and 10mVPP signal
Everything look like it is the correct region, MOSFET=Saturation, BJT=Active, maybe I am wrong
Add Rs to stabilize circuit, temperature seems to have some impact
Are the PSpice components design correctly? Given to us by instructor but are they accurate enough?
Will balancing the BJT bias help?
MOSFET is 620k||500K in PSpice for the same DC values through the entire system I need 639k||300K. In PSpice the actual best seem to be a ratio of the PSpice numbers.
Thanks,
asdfrewq