Analog Multiplier - Variable Transconductance Technique | Linear Integrated Circuits : Analog Multiplier and PLL
Chapter: Linear Integrated Circuits : Analog Multiplier and PLL
Variable Transconductance Technique
Variable
Transconductance Technique:
·
The
variable transconductance technique makes use of the dependence characteristic
of the transistor transconductance parameter on the emitter current
bias applied. A simple differential circuit arrangement depicting the principle
is shown in figure.
·
The
relationship between V0 and Vx . is given by V0
= gm RL VX where gm = IEE /VT is
the transconductance of the stage.
·
Application
of a second input Vy to the reference current source of the
differential amplifier can vary gm.
·
Thus,
if RE IEE >>VBE, the bias voltage Vy is
related to IEE by the relation Vy = IEE RE.
·
Then,
the overall voltage transfer expression is given by
V0 = gm RLVx = (Vy/VTRE)VxRL
=
VxVy RL/ VTRE
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