allpass filters

  • Thread starter Alessandro Esposito
  • Start date
A

Alessandro Esposito

Guest
HI need to shift the phase of a signal between 0 to 180°. I usually work
with sinuswave between 10KHk and 100MHz.
I found out it is possbile to build a so called allpass filter to make this:

R1
+----\/\/\-+
| -\ |
R1 | | \ |
+-\/\/\+-|- \ |
Vin ---+ | >--+--- Vout
+-\/\/\+-|+ /
C | | /
| -/
\
/ R2
\
|
GROUND

in which R2 is variable and control the phase delay.

I have to question:

1) I do not have formulas to setup the values of C and Ri... is, for
example, R1 the input impedence of the circuit?
2) Is it possible to use this circuit up to 100MHz? Which opamp could work?

A less important aspect:
I would like to modify this phase via a PC: Do you think is is reliable the
use of a DAC to control the voltage on a FET base to use it instead (or
with) R2?

Thanks
Alessandro
 
R1
+----\/\/\-+
| -\ |
R1 | | \ |
+-\/\/\+-|- \ |
Vin ---+ | >--+--- Vout
+-\/\/\+-|+ /
C | | /
| -/
\
/ R2
\
|
GROUND
 
Sorry... I am not drunked!!! :)

R1
+----\/\/\-+
| -\ |
R1 | | \ |
+-\/\/\+-|- \ |
Vin ---+ | >--+--- Vout
+--||--+-|+ /
C | | /
| -/
\
/ R2
\
|
GROUND
 
R1
+----\/\/\-+
| -\ |
R1 | | \ |
+-\/\/\+-|- \ |
Vin ---+ | >--+--- Vout
+---||-+-|+ /
C | | /
| -/
\
/ R2
\
|
GROUND
"Alessandro Esposito" <theopps75@yahoo.it> wrote in message news:boodlu$nlv$1@gwdu112.gwdg.de...
R1
+----\/\/\-+
| -\ |
R1 | | \ |
+-\/\/\+-|- \ |
Vin ---+ | >--+--- Vout
+-\/\/\+-|+ /
C | | /
| -/
\
/ R2
\
|
GROUND
 
You beat me to it!
"Lord Garth" <LGarth@Tantalus.net> wrote in message news:iXOrb.2291$ws7.701@newssvr24.news.prodigy.com...
R1
+----\/\/\-+
| -\ |
R1 | | \ |
+-\/\/\+-|- \ |
Vin ---+ | >--+--- Vout
+---||-+-|+ /
C | | /
| -/
\
/ R2
\
|
GROUND
"Alessandro Esposito" <theopps75@yahoo.it> wrote in message news:boodlu$nlv$1@gwdu112.gwdg.de...
R1
+----\/\/\-+
| -\ |
R1 | | \ |
+-\/\/\+-|- \ |
Vin ---+ | >--+--- Vout
+-\/\/\+-|+ /
C | | /
| -/
\
/ R2
\
|
GROUND
 
yep of 4 minutes!!!!!
Did I win the answer? :)

"Lord Garth" <LGarth@Tantalus.net> wrote in message news:DZOrb.2295$Mf7.1298@newssvr24.news.prodigy.com...
You beat me to it!
"Lord Garth" <LGarth@Tantalus.net> wrote in message news:iXOrb.2291$ws7.701@newssvr24.news.prodigy.com...
R1
+----\/\/\-+
| -\ |
R1 | | \ |
+-\/\/\+-|- \ |
Vin ---+ | >--+--- Vout
+---||-+-|+ /
C | | /
| -/
\
/ R2
\
|
GROUND
"Alessandro Esposito" <theopps75@yahoo.it> wrote in message news:boodlu$nlv$1@gwdu112.gwdg.de...
R1
+----\/\/\-+
| -\ |
R1 | | \ |
+-\/\/\+-|- \ |
Vin ---+ | >--+--- Vout
+-\/\/\+-|+ /
C | | /
| -/
\
/ R2
\
|
GROUND
 
"Alessandro Esposito" <theopps75@yahoo.it> wrote in message news:booehj$pd5$1@gwdu112.gwdg.de...
yep of 4 minutes!!!!!
Did I win the answer? :)


Sorry, I don't know. :-(
 
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