High Voltage OP amp...

[Trevor Wilson]

I am servicing a power amplifier which uses a dual, 8 pin DIP OP amp.
Unfortunately, the rail Volts on the OP amp (LF353) is +/- 22 Volts. I
am familiar with this particular amplifier and OP amp failure is quite a
frequent thing. I need a suggested replacement. I am quite happy to use
single OP amps, or SOICs, as I can employ a Brown Dog carrier to adapt
to the existing layout. Ideally, a bit more performance over the LF353
would be nice.

And no, it is not possible to drop the rail Voltages. They must remain
at +/-22 Volts.

TIA


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[kayge]

On Sat, 03 Sep 2022 14:34:44 +1000, Trevor Wilson wrote:

I am servicing a power amplifier which uses a dual, 8 pin DIP OP amp.
Unfortunately, the rail Volts on the OP amp (LF353) is +/- 22 Volts. I
am familiar with this particular amplifier and OP amp failure is quite a
frequent thing. I need a suggested replacement. I am quite happy to use
single OP amps, or SOICs, as I can employ a Brown Dog carrier to adapt
to the existing layout. Ideally, a bit more performance over the LF353
would be nice.

And no, it is not possible to drop the rail Voltages. They must remain
at +/-22 Volts.

TIA

Hello, TI\'s OPA552UA has up to +/-30V rails and a bit better slew rate
(24V/uS)although it\'s a bit noisier. You may find a dual version of this
at TI.

 

[Phil Hobbs]

Trevor Wilson wrote:

I am servicing a power amplifier which uses a dual, 8 pin DIP OP amp.
Unfortunately, the rail Volts on the OP amp (LF353) is +/- 22 Volts. I
am familiar with this particular amplifier and OP amp failure is quite a
frequent thing. I need a suggested replacement. I am quite happy to use
single OP amps, or SOICs, as I can employ a Brown Dog carrier to adapt
to the existing layout. Ideally, a bit more performance over the LF353
would be nice.

And no, it is not possible to drop the rail Voltages. They must remain
at +/-22 Volts.

TIA

What\'s the required output swing? A baby board with one or two zeners
in the supply leads (plus a 100 nF-ish bypass between them) is pretty
easy, at least if you get these things in a lot.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[Trevor Wilson]

On 4/09/2022 5:06 am, Phil Hobbs wrote:

Trevor Wilson wrote:
I am servicing a power amplifier which uses a dual, 8 pin DIP OP amp.
Unfortunately, the rail Volts on the OP amp (LF353) is +/- 22 Volts. I
am familiar with this particular amplifier and OP amp failure is quite
a frequent thing. I need a suggested replacement. I am quite happy to
use single OP amps, or SOICs, as I can employ a Brown Dog carrier to
adapt to the existing layout. Ideally, a bit more performance over the
LF353 would be nice.

And no, it is not possible to drop the rail Voltages. They must remain
at +/-22 Volts.

TIA

What\'s the required output swing?  A baby board with one or two zeners
in the supply leads (plus a 100 nF-ish bypass between them) is pretty
easy, at least if you get these things in a lot.

Cheers

Phil Hobbs

**I need maximum output Voltage swing. Hence the designer (now deceased)
chose a +/- 22 Volt supply. Hence the need for higher Voltage OP amps.


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[Trevor Wilson]

On 4/09/2022 4:31 am, kayge wrote:

On Sat, 03 Sep 2022 14:34:44 +1000, Trevor Wilson wrote:

I am servicing a power amplifier which uses a dual, 8 pin DIP OP amp.
Unfortunately, the rail Volts on the OP amp (LF353) is +/- 22 Volts. I
am familiar with this particular amplifier and OP amp failure is quite a
frequent thing. I need a suggested replacement. I am quite happy to use
single OP amps, or SOICs, as I can employ a Brown Dog carrier to adapt
to the existing layout. Ideally, a bit more performance over the LF353
would be nice.

And no, it is not possible to drop the rail Voltages. They must remain
at +/-22 Volts.

TIA

Hello, TI\'s OPA552UA has up to +/-30V rails and a bit better slew rate
(24V/uS)although it\'s a bit noisier. You may find a dual version of this
at TI.

**Thanks for that. I can probably live with a higher noise level. I like
the idea of a higher speed OP amp.

I found a couple available locally, though there is a long lead time for
more. I can live with that.

Thanks for the tip.



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[Phil Allison]

Trevor Wilson wrote:
=================

I am servicing a power amplifier which uses a dual, 8 pin DIP OP amp.
Unfortunately, the rail Volts on the OP amp (LF353) is +/- 22 Volts.

** That is a mistake, all versions of the Sumo 9 used nominal +/-20V rails fed from series regs with 20V zeners.

> I need a suggested replacement.

** Which MUST be a FET input op-amp.


> And no, it is not possible to drop the rail Voltages.

**Course it is, they are meant to be 19.5V each anyway.

> They must remain at +/-22 Volts.

** Humbug.

...... Phil

 

[Phil Hobbs]

Trevor Wilson wrote:

On 4/09/2022 5:06 am, Phil Hobbs wrote:
Trevor Wilson wrote:
I am servicing a power amplifier which uses a dual, 8 pin DIP OP amp.
Unfortunately, the rail Volts on the OP amp (LF353) is +/- 22 Volts.
I am familiar with this particular amplifier and OP amp failure is
quite a frequent thing. I need a suggested replacement. I am quite
happy to use single OP amps, or SOICs, as I can employ a Brown Dog
carrier to adapt to the existing layout. Ideally, a bit more
performance over the LF353 would be nice.

And no, it is not possible to drop the rail Voltages. They must
remain at +/-22 Volts.

TIA

What\'s the required output swing?  A baby board with one or two zeners
in the supply leads (plus a 100 nF-ish bypass between them) is pretty
easy, at least if you get these things in a lot.


**I need maximum output Voltage swing. Hence the designer (now deceased)
chose a +/- 22 Volt supply. Hence the need for higher Voltage OP amps.

Sure, but typically not everything in a circuit needs to swing the full
supply range. You\'re losing at least a couple of V_BEs on each end
now--in fact the LF353 datasheet minimum output swing is +-3 V from the
rails (+-12 on +-15 supplies) even at light loads.

There are nice things in the 40V range such as the MC34072, which
typically swings +14 to -14.7 off +-15 if fairly lightly loaded. It\'s
also a lot quieter than the LF353, not that you probably care much in a
power amp.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[Trevor Wilson]

On 4/09/2022 10:28 am, Phil Allison wrote:

Trevor Wilson wrote:
=================
I am servicing a power amplifier which uses a dual, 8 pin DIP OP amp.
Unfortunately, the rail Volts on the OP amp (LF353) is +/- 22 Volts.

** That is a mistake, all versions of the Sumo 9 used nominal +/-20V rails fed from series regs with 20V zeners.

**Oops. You are correct. The negative rail is fed from a 20 Volt zener
and the positive rail is fed from a series transistor, with the base
tied to a 20 Volt zener, in series with a forward biased diode.

I need a suggested replacement.

** Which MUST be a FET input op-amp.

**Yes. There is that.

And no, it is not possible to drop the rail Voltages.

**Course it is, they are meant to be 19.5V each anyway.

They must remain at +/-22 Volts.

** Humbug.

**True enough. I had neglected to examine the schematic before I posted.
According to the schem, it is +/- 20 Volts.



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