Biomedical Engineering Reference
In-Depth Information
Fig. 6
Simulation results of
low noise amplifier (LNA) S
11
and S
21
versus C
2
variation
Fig. 7
Schematic of the
squarer
Squarer
The schematic of the proposed squarer is shown in Fig.
7
[
13
]. Transistors NM
1
−
4
have the same sizing and the same DC biasing point in saturation region. Differential
RF input signals are fed into NM
1
−
2
to perform squaring function while NM
3
−
4
are
AC grounded, so as to cancel the output DC components. The total biasing current
is set by the current source
I
bias
.NM
5
−
6
are cascode stages to enhance the squarer
output impedance. Large output impedance is desired to boost the output voltage
swing, hence active load is used here using PMOS transistors PM
1
−
2
and they are
biased with a common-mode feedback (CMFB) circuit. It is well known that active
load value decreases with increasing frequency due to the large parasitic capacitance.
Search WWH ::
Custom Search