Audio Amplifier and AGC?
Bryan Speed
jnt...@lion.ee.vt.edu (John Tilki) wrote:
> Can anyone suggest an audio amplifier circuit or chip to take the
>output of an electret microphone (about 30mV peak swing) and cleanly
Get National Semiconductors Linear Applications handbook. The subject
is discussed.
>applications. Also, can anyone suggest an automatic gain control
>circuit or chip to maintain the output at about the 1.5V peak swing
>level? There is one important constraint for both the amplifier and
The MC3340 audio agc chip.
The LM358 opamp will work well for the agc dc amp. It senses signals
near ground on the input and pulls linearly to (nearly) ground on the
output which will help with the dynamic range with a 5v supply.
Otherwise use a voltage double in the design..:)
..B
Tom Loredo
Hi-
Analog Devices has a new chip in their SSM series of
audio chips that I believe does just this: a combined
mic preamp and AGC. Check their web site:
Although hobbiest suppliers like Jameco and JDR carry
some AD parts, for this one you are likely to have to
order through Allied or Newark. Allied is available
online at:
Good luck!
-Tom Loredo
The2X4
I've mis-matched impedances and got poor performance. Just a thought.
RCA might have what you need.
Can't think of the number -CA 30xx something.
Have you checked the Motorola site? Texas Ins? National Semi?
I looked in the Graf VOl 3 book. Nothing.
Carl
John Tilki
Can anyone suggest an audio amplifier circuit or chip to take the
output of an electret microphone (about 30mV peak swing) and cleanly
do NOT want the basic op-amp circuits to provide the gain. These have
been tried and do not perform well enough. Rather what I am interested
in is perhaps a preamplifier chip designed for such low-noise high-gain
applications. Also, can anyone suggest an automatic gain control
circuit or chip to maintain the output at about the 1.5V peak swing
level? There is one important constraint for both the amplifier and
commercial products that use electret microphones for audio, I am sure
cookbook solutions to this problem must exist. Thank you in advance
for any insight or information you can provide.
--
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John F. Tilki, Ph.D. Student
Bradley Department of Electrical Engineering
Virginia Polytechnic Institute and State University
Blacksburg, VA 24061-0111
Digital Signal Processing Research Lab: (540)231-3069
Home: (540)951-7759 Email: ti...@vt.edu Fax: (540)951-7759
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Rene Zuidema
On 9 Sep 1996 18:36:41 GMT, jnt...@lion.ee.vt.edu (John Tilki) wrote:
> Can anyone suggest an audio amplifier circuit or chip to take the
>output of an electret microphone (about 30mV peak swing) and cleanly
>amplify it by about a factor of 50 (to about a 1.5V peak swing). I
>do NOT want the basic op-amp circuits to provide the gain.
Check ham radio magazines. I had a design printed in two magazines
involving a transistor (BC547-like), a 741 grade opamp, 4 1N4148's and
some R / C's. Diodes were used in a DC operated attenuation feedback
bridge (NO clipper!). 40 dB dynamic range, Input 0.5 - 50 mV, out ~1 V
p/p. Ultra-cheap.
I cannot do it in ascii art, but if you can provide a fax number...
But there must be tons of alternatives to be found.
Best Regards, Rene.
<All opinions expressed here are mine, >
<unless you dislike them. >
Mark Zenier
in <511o3p$o...@solaris.cc.vt.edu>, John Tilki wrote:
: Can anyone suggest an audio amplifier circuit or chip to take the
: output of an electret microphone (about 30mV peak swing) and cleanly
: amplify it by about a factor of 50 (to about a 1.5V peak swing). I
: been tried and do not perform well enough. Rather what I am interested
: in is perhaps a preamplifier chip designed for such low-noise high-gain
: applications. Also, can anyone suggest an automatic gain control
: circuit or chip to maintain the output at about the 1.5V peak swing
: level?
There is an preamp with alc, TA7137P, a japanese chip in a sip package.
From Toshiba. It in the NTE replacement line as an NTE1466, and
probably in the ECG series as well.
It's what the baby monitor transmitter that I use as wireless headphones
has for the audio stage. Doesn't seem to mind that it's getting a direct
connection to a line level signal from a shortwave receiver instead of
the built in electret mic.
Mark Zenier mze...@eskimo.com mze...@netcom.com
John Lundgren
John Tilki (jnt...@lion.ee.vt.edu) wrote:
: Can anyone suggest an audio amplifier circuit or chip to take the
: output of an electret microphone (about 30mV peak swing) and cleanly
: amplify it by about a factor of 50 (to about a 1.5V peak swing). I
: do NOT want the basic op-amp circuits to provide the gain. These have
: been tried and do not perform well enough. Rather what I am interested
: in is perhaps a preamplifier chip designed for such low-noise high-gain
: applications. Also, can anyone suggest an automatic gain control
: circuit or chip to maintain the output at about the 1.5V peak swing
: the AGC -- the only power supply available is +5V. Given the number of
: commercial products that use electret microphones for audio, I am sure
: cookbook solutions to this problem must exist. Thank you in advance
: for any insight or information you can provide.
The compressors that I've seen use a single transistor amplifier with a
high value emitter resistor. This resistor is bypassed by a capacitor
with a JFET in series with the ground lead. THe output is rectified and
the negative voltage is applied to the gate of the FET, so the higher the
output the more resistance the FET has. THe circuit usually needs another
simple amp before the rectifier. I think the compression is about 20 dB.
: --
: ----------------------------------------------------------------
: John F. Tilki, Ph.D. Student
: Bradley Department of Electrical Engineering
: Virginia Polytechnic Institute and State University
: Blacksburg, VA 24061-0111
: Digital Signal Processing Research Lab: (540)231-3069
: Home: (540)951-7759 Email: ti...@vt.edu Fax: (540)951-7759
: ----------------------------------------------------------------
--
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Wouter Suverkropp
jlun...@delta1.deltanet.com (John Lundgren) wrote:
>John Tilki (jnt...@lion.ee.vt.edu) wrote:
>: Can anyone suggest an audio amplifier circuit or chip to take the
>: output of an electret microphone (about 30mV peak swing) and cleanly
>: amplify it by about a factor of 50 (to about a 1.5V peak swing). I
>: do NOT want the basic op-amp circuits to provide the gain.
Use a AD6270 chip. It is a VOGAD, used in telecomms circuits to provide an essentially
flat output level over an input variation of 60 dB. Takes electret microphones directly
on its input. Not 100% certain about the AD prefix. You can set attack and decay time, and
add some filtering with this 8-pin device.
Good luck,
Wouter
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For direct E-Mail please respond to Wouter.S...@jet.uk
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The above article is the personal view of the poster and should not be
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Tom Loredo
I don't recall the details (eg, power supply range), but Analog
Devices has some recent chips in their SSM audio series
that combine a mic preamp and AGC on the same chip. Check
their web site, http://www.analog.com/
Good luck!
-Tom Loredo
Leon Heller
In article <51raai$l...@postman.jet.uk>
Wouter.S...@jet.uk "Wouter Suverkropp" writes:
> jlun...@delta1.deltanet.com (John Lundgren) wrote:
> >John Tilki (jnt...@lion.ee.vt.edu) wrote:
> >: Can anyone suggest an audio amplifier circuit or chip to take the
> >: output of an electret microphone (about 30mV peak swing) and cleanly
> >: amplify it by about a factor of 50 (to about a 1.5V peak swing). I
> >: do NOT want the basic op-amp circuits to provide the gain.
>
> Use a AD6270 chip. It is a VOGAD, used in telecomms circuits to provide an
> essentially
> flat output level over an input variation of 60 dB. Takes electret microphones
> directly
> on its input. Not 100% certain about the AD prefix. You can set attack and
> decay time, and
> add some filtering with this 8-pin device.
It's actually SL6270, made by GPS (formerly Plessey). GPS seem to be
dropping some of the old Plessey chips, so it might not be available for
much longer.
Leon
--
Leon Heller, G1HSM | "Do not adjust your mind, there is
E-mail le...@lfheller.demon.co.uk | a fault in reality": on a wall
Phone: +44 (0)1734 471424 | many years ago in Oxford.
Chris Grant
> jlun...@delta1.deltanet.com (John Lundgren) wrote:
> >John Tilki (jnt...@lion.ee.vt.edu) wrote:
> >: Can anyone suggest an audio amplifier circuit or chip to take the
> >: output of an electret microphone (about 30mV peak swing) and cleanly
> >: amplify it by about a factor of 50 (to about a 1.5V peak swing). I
> >: do NOT want the basic op-amp circuits to provide the gain.
>
> Use a AD6270 chip. It is a VOGAD, used in telecomms circuits to provide an
> essentially
> flat output level over an input variation of 60 dB. Takes electret microphones
> directly
> on its input. Not 100% certain about the AD prefix. You can set attack and
> decay time, and
> add some filtering with this 8-pin device.
>
> Good luck,
>
> Wouter
>
> ====================================================================
> For direct E-Mail please respond to Wouter.S...@jet.uk
>
> ===============================================================================
> The above article is the personal view of the poster and should not be
> considered as an official comment from the JET Joint Undertaking
> ===============================================================================
>
The 6270 is a GPS (Plessey) ic, one of the many that have been withdrawn.
Chris Grant
Booth, Thomas G
In article <32419803...@spacenet.tn.cornell.edu>, Tom Loredo
Tom, the device you're referring to is the SSM2165, and there is indeed a
.pdf file of the preliminary data sheet @ Analog Devices' Web site. I've
taken a brief look at the data sheet, and I'm not sure if John Tilki will
be satisfied w/ the device...IMO the 1 kHz input noise voltage spec of < 20
nV/sqrt(Hz) guaranteed, 14 nV/sqrt(Hz) typical is a bit high, and there's
no input noise current spec given, which makes a decent noise analysis a
bit tough.
Hopefully John Tilki has considered self-noise in his condenser microphone,
particularly if he will be using a capsule which has an integral FET
impedance converter. Some of the low-cost mic capsules w/ FET converters
aren't the best performers in terms of self-noise, and will be the limiting
factor in overall S/N performance.
TGB
\\ The opinions expressed herein are my own. //
Booth, Thomas G
Reposting article removed by rogue canceller.
Michael Bender
Tom Loredo (lor...@spacenet.tn.cornell.edu) wrote:
: I don't recall the details (eg, power supply range), but Analog
: Devices has some recent chips in their SSM audio series
: that combine a mic preamp and AGC on the same chip. Check
: their web site, http://www.analog.com/
Check out the SSM2165 (among others).
mike
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