sec,
Building an analog multiplier from discrete transistors is impractical because of the tight parameter matching required (Look up "Gilbert Cell" on the web).
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You can build a 2 quadrant multiplier from an Op amp or comparator by using a pulse width modulation scheme. to control the on time of an analog switch, and filtering the output.
Regards,
Kral
Basically a multiplier output is Z=X*Y and it could be allso Z(t)=X(t)*Y(t). Amplitude modulation formula has the same structure and it follows that multiplier can be used as amplitude modulator.
More about analog multiplier and how it can be used you can find in datasheet for MC1495.
Four quadrant means that both variables X and Y can have positive or negative sign. Two quadrant means that one of the variables can have only one sign and other both signs. Use the analogy with cartesian plane.
Usually analog multipliers based on differential current dividers which ruled by input voltage,or current dividers which ruled by input current from v-to-i converters.
But these schemes have low accuracy.
For high precision you can use ADC with multiplying DAC
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sec,
As Borber pointed out, an analaog multiplier can be used as an AM modulator. However, the DC characteristics, such as DC offset usually are not important in an AM modulator.
Regards,
Kral
Borber is right, of course. However, in a modulator application, capacitor coupling can be used to eliminate DC offsets, unless the modulation components must really go down to DC.
Four quadrant multiplier is better because only multiplier offsets, which are small are producing parasitics. Two quadrant multiplier can be used where ωm can have DC offset.
can anyone has analog multiplier circuit then do send me
also if u have C coding to build the analog multiplier then multiplies the signal and NRZ level and phase shifter bcoz my proj is BPSK modulator SO SEND ME THE CODING AND CKT
THANX
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