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from the conventional differential amplifier, in that in a conventional circuit, the same
current flows in the input and load transistors, while in the proposed circuit, the
currents in the input and load transistors are I C1 /2 and I C2 /2, respectively, which are
not equal; and it is by controlling these two currents by the control voltage, by the
circuit of Fig. 1, that a wide dynamic range VGA is obtained.
V DD
M 1
M 4
M 3
I O
V C
I C1
I C2
C 1
C 2
M 2
M 5
M 6
I O
V SS
Fig. 1. Circuit diagram of control stage [2]
V C
Fig. 2. Decibel scale plot of current ratio √ (I C2 /I C1 ) of control circuit
 
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