ISSN 10637397, Russian Microelectronics, 2014, Vol. 43, No. 7, pp. 459–461. © Pleiades Publishing, Ltd., 2014.
Original Russian Text © E.O. Belousov, A.G. Timoshenko, 2013, published in Izvestiya Vysshikh Uchebnykh Zavedenii. Elektronika, 2013, No. 4(102), pp. 24–27.
A variable gain amplifier (VGA) is used in trans
ceivers, CDROM drives, TV receivers [1–4], etc. In
superheterodyne receivers, wherein a signal after the
detection by an antenna must be amplified up to the
peaktopeak value relative to the reference voltage
of a digitizer, a VGA is employed as a part of a circuit
of signal processing at an intermediate frequency .
The signal strength at the input of a receiver can vary
in accordance with the distance to a transmitter. To
eliminate the feasibility of the transition to the satu
ration for the next stages of the circuit, the gain
adjustment range must be large. Such an amplifier
must have a large bandwidth for any control value in
order to be able to operate with wideband signals.
On the one hand, circuits of CMOS amplifiers with
a wide gain adjustment range [1, 2] have the small
bandwidth and are unsuitable for operating with wide
band signals; on the other hand, these amplifiers have
a small Gain adjustment range.
In this paper, we present an amplifier with a wide
gain adjustment range, a large bandwidth, and an to
input impedance matched 50
. A wide gain adjust
ment range is attained by using a circuit of the Com
mon mode feedback (CMFB) in each variable gain
STUDYING AND DEVELOPING NODES
OF A VGA
One variant of a variable gain stage is a differential
amplifier with a diode load and
channel inputs 
(Fig. 1a). The Gain of each branch of this circuit is
From (1) we can conclude that when transistors of
a circuit are found in a active region the gain depends
only on the ratio of the transconductance of the input
transistor to the transconductance of the load transis
tor. The gain of the circuit is varied by changing the
Method for Extending the Bandwidth of Variable Gain Amplifiers
E. O. Belousov and A. G. Timoshenko
National Research University of Electronic Technology MIET, proezd 4806 5, Zelenograd, Moscow, 124498 Russia
Received April 16, 2013
—A variable gain amplifier for use in the automatic gain control system of a radio receiver is consid
ered. The method of extending the bandwidth for processing wideband signals at an intermediate frequency
in operations with signals of the millimetric wave band is presented.
Variablegain stage: (a) a diodeload amplifier and (b) a CMFB circuit.