Re: Best op amp for wien bridge oscillator for highest BW.

On 5 Feb, 15:17, Patrick Turner <i...@xxxxxxxxxxxxxxxxxx> wrote:
This morning I well and truly fried a signal generator beyond
fixability.

Solid state generators don't like +580Vdc poked down their outputs, but
I managed it while testing a Dynaco MK6.

There was a sickening sausage sizzle sound as a a bunch of parts
converted quickly from plastic encased silicon to soot.

So, I am re-building a 5 range wien bridge oscillator to go from 2Hz to
200kHz.

So far, with NE5534 and with +/-6V rails I can just get the five full
ranges but only 2.8Vrms output. Using higher rails above 9V up to 12V
means the op amp struggles above 100kHz and the oscilations break up
into a series of bursts rather than continuous nice oscillations.

So what's the best opamp for wide bandwidth?

Positive FB networks have caps ranging from 4.7uF to 470pF, and variable
R from 1k5 to 16k.

NFB network is about 200 ohms plus two series tiny lamps which when
warmed are 100 ohms, or just right.

With 11V rails I got 5.6V at below 50kHz OK with the NFB ohms totaling
only 133 ohms with one lamp which means the opamp must move into class
AB operation to do this because at idle the Idc = 11mA.

I'd like 5 Vrms at 200kHz or higher F if I can get it.

Any thoughts?

Patrick Turner.

This could be interesting Patrick,
I am also playing about and gathering parts for a nice Wein bridge
oscilator. It seems that the NE5532/4 is are hard act to beat. Check
out this page on Doug. Selfs site:
http://www.dself.dsl.pipex.com/ampins/webbop/opamp.htm
There are a lot of new opamps about now but I m not really up to speed
on them.A couple I have been looking at are the LME49710 and 49720 and
their cousin the 49600 as a buffer. They are expensive though and the
NE5532/4 seems to be the best bang for your buck as they say.
Matt.
.

Relevant Pages

  • Re: AR9 speakers from about 1980.
    ... Patrick Turner wrote... ... > I measured the bass voice coil dcr, ... > The dcr of the series inductors is about 2 ohms. ... Got a H-K Citation Amp? ...
    (rec.audio.tubes)
  • Best op amp for wien bridge oscillator for highest BW.
    ... Solid state generators don't like +580Vdc poked down their outputs, ... with NE5534 and with +/-6V rails I can just get the five full ... NFB network is about 200 ohms plus two series tiny lamps which when ... warmed are 100 ohms, or just right. ...
    (rec.audio.tubes)
  • Re: thermocouple input, 0..20mA output
    ... Normal opamps can't touch the rails and I didn't like ... The opamp tries to match the 16mv difference and raises its output. ... >> The 1k is a currrent limiting resistor to protect the NPN transistor. ... >> Measure the polarity of the thermocouple while holding it in a flame. ...
    (sci.electronics.design)
  • Re: Opinions on SE output tube sought
    ... in article 4A13D634.C9365898@xxxxxxxxxxxxxxxxxx, Patrick Turner at ... A few years ago I designed a simple headphone amplifier for a neighbor, ... and the primary resistance is 237 ohms. ... If you had a 5k load on the output tube, the match at the sec would be ...
    (rec.audio.tubes)
  • Re: 3.3v robustness
    ... CMOS Opamp configured as a differential amp with the inputs connected ... If I add clamp diodes from the opamp inputs to the rails ... Why don't you put the op amp close to the strain gauge? ... The strain gauge is in a high temperature environment which is too hot ...
    (sci.electronics.design)