Analog Multiplier - Gilbert Multiplier cell | Linear Integrated Circuits : Analog Multiplier and PLL
Chapter: Linear Integrated Circuits : Analog Multiplier and PLL
Gilbert Multiplier cell
Gilbert
Multiplier cell:
The
Gilbert multiplier cell is a modification of the emitter coupled cell and this
allows four – quadrant multiplication. Therefore, it forms the basis of most of
the integrated circuit balanced Multipliers. Two cross- coupled emitter-
coupled pairs in series connection with an emitter coupled pair form the
structure of the Gilbert multiplier cell.
The
collector current of Q3 and Q4 are given by
Similarly,
the collector current of Q5 and Q6 are given by
collector current IC1 and IC2
of transistors Q1 and Q2 can be expressed as
Substituting
the above equation in IC3 and IC4, we get
Similarly
substituting Ic2= in Ic5 and IC6 , we get,
The
differential output current I is given by
∆I
=IL1 - IL2
=
(IC3 +IC5) - ( IC4+IC6)
=IC3
- IC6)-(IC4 - IC5)
∆I=IEE
tanh( V1/2VT) tanh(V2/2VT)
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