Please help me to determin the Total Harmonic Distortion of this amplifier
This design is drawn in Orcad 9.2.
Orcad can determin this, and how?
An externally hosted image should be here but it was not working when we last tested it.
This design is drawn in Orcad 9.2.
Orcad can determin this, and how?
If I remember correctly the free demo version won't handle that many parts
a full licensed version of ORCAD could sim the circuit and in principle calc thd #, noise modeling is also possible but you'll need realistic transistor noise spice models
Linear Technology's LtSpice is a free Spice that I use exclusively in preference to the limited OrCad demo version, you do have to hunt down part models and add to the small lib distributed with LtSpice
but as someone who likes simulating amplifiers I haven't ever tried to calc thd # because it gives little insight into circuit performance
even the simulated intermodulation harmonic distortion spectrum analysis that I prefer are far from predicting real amplifier harmonic distortion due to the lack of realistic transistor models and the inability to easily handle realistic thermal effects in the output Qs in Spice
A Spice model of a circuit is a useful tool, when you can get paper calcs and approximations to reconcile with sim results - and understand the limitations of both then you are in a better position to debug and verify operation of the hardware prototypes
simulation should show you some problems with the bias levels in the circuit you show - although a common spice transistor model flaw is a ridiculously high hfe (and always matched between same model #) which could hide the bias problems
a full licensed version of ORCAD could sim the circuit and in principle calc thd #, noise modeling is also possible but you'll need realistic transistor noise spice models
Linear Technology's LtSpice is a free Spice that I use exclusively in preference to the limited OrCad demo version, you do have to hunt down part models and add to the small lib distributed with LtSpice
but as someone who likes simulating amplifiers I haven't ever tried to calc thd # because it gives little insight into circuit performance
even the simulated intermodulation harmonic distortion spectrum analysis that I prefer are far from predicting real amplifier harmonic distortion due to the lack of realistic transistor models and the inability to easily handle realistic thermal effects in the output Qs in Spice
A Spice model of a circuit is a useful tool, when you can get paper calcs and approximations to reconcile with sim results - and understand the limitations of both then you are in a better position to debug and verify operation of the hardware prototypes
simulation should show you some problems with the bias levels in the circuit you show - although a common spice transistor model flaw is a ridiculously high hfe (and always matched between same model #) which could hide the bias problems
Run the simulator of course... 
If memory serves:
Click on Transient Analysis, put in a decent analysis time (start at 0, simulate for say 20mS).
Go over to the waveform display tab, and select the node number that represents the output of your amplifier. You should see a sine-wave (since your input was a sine wave).
This is where my memory is really fuzzy, but there should be something in the waveform display that you can select to make it do a Fourier or spectrum analysis...
Cheers!
If memory serves:
Click on Transient Analysis, put in a decent analysis time (start at 0, simulate for say 20mS).
Go over to the waveform display tab, and select the node number that represents the output of your amplifier. You should see a sine-wave (since your input was a sine wave).
This is where my memory is really fuzzy, but there should be something in the waveform display that you can select to make it do a Fourier or spectrum analysis...
Cheers!
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