|
CLC408 Datasheet, PDF (10/12 Pages) National Semiconductor (TI) – Comlinear CLC408 High-Speed, Low-Power Line Driver | |||
|
◁ |
where GBWPU1 is the Gain-Bandwidth Product of
U1. As R3 is made larger, fUG becomes smaller. fUG
should be large enough so that U2âs 1/f noise does not
significantly impact the output noise.
Adjust R7 so that the gain at f << fUG matches the gain at
f >> fUG.
Precision Half-Wave Rectifier
Figure 8 shows a precision half-wave rectifier. When
Vin > 0, D1 is on and D2 is off. When Vin < 0, D1 is off and
D2 is on. The second amplifier (U2) buffers Vo from the
variable output impedance of the rectifier.
The output voltage is:
0, Vin < 0
Vo
=

â

R2
R1
â
ï£ï£¬1+
R6
R5


â
Vin,
Vin
>
0
Vin R1
R2
R4
-
D1
CLC408
+ U1
D2
R3
+
Vo
CLC408
- U2
R6
R5
Diodes D1 and D2 need to be Schottky or PIN diodes to
minimize delay.
Set R2 = R3 to the recommended feedback resistor value
for the gain Av = -R2/R1. R2 and R3 may need to be
increased slightly to compensate for the delays through
D1 and D2.
Set R6 to the recommended feedback resistor value for
the gain Av = (1 + R6/R5).
R4 is an optional resistor; it helps isolate U2âs input from
the changing output impedance of U1.
Other configurations are possible:
1) Connect U2âs input between R3 and D2 so that
Vo â 0 for Vin < 0.
2) Use an inverting gain configuration for U2 to
change the polarity of Vo.
Pick the combination that best suits your needs.
Figure 8: Precision Half-Wave Rectifier
http://www.national.com
10
|
▷ |