Sub for TL071

[Guest Kasamiko]

Need a good sub for TL071..
LMxxx will do..

rhonn  ;) ;)

[audioguru]

Hi Rhonn,
National doesn't make a single low-noise equal the the TL071 but they have a dual LM833 that is very low-noise and wideband for audio. It has transistors for inputs not the FETs of the TL07x series. ;D

[Guest Kasamiko]

John do I really need a very low noise device for this?



What can you say?

rhonn

[audioguru]

Hi Rhonn,
You're making an AC voltmeter with a gain of only 10, so I don't think you would notice the noise from a "regular" opamp such as a TL081.
The circuit needs a FET input opamp like the TL071 and TL081 because of the circuit's high resistor values at its input divider.
The 100kHz bandwidth on the project's X1 range might be nice, but the capacitance in the divider will reduce the circuit's bandwidth in higher ranges.

National discontinued their FET input and wideband LF351 about 12 years ago but maybe you can find some. ;D

[hotwaterwizard]

Here is the Datasheet.

TL071_TL072_TL074.pdf

[Guest Kasamiko]

.....National discontinued their FET input and wideband LF351 about 12 years ago but maybe you can find some. ;D

Ohhh I still got a dozen of this gem (LF351).. ;D
Can I used LF351 as a direct replacement for TL071?

@John
Thanks for the datasheet..

BTW:
Where can I find a link for DIY X1 oscilloscope probe? I'm planning to built one.

rhonn  ;) ;)

[EdwardM]

Hi Kasamiko

take a look at this

Ed

http://www.emcesd.com/1ghzprob.htm

[audioguru]

Can I use LF351 as a direct replacement for TL071?

Sure, your application is perfect for it.

Where can I find a link for DIY X1 oscilloscope probe? I'm planning to built one.

Low-capacitance shielded cable, a ballpoint pen casing and a stiff pointed end is all you need.
I use tiny alligator clips on the end of low-cap cable for my old 5MHz 'scope.

Are you going to look at the 240VAC output of inverters? ;D

[audioguru]

Hi Rhonn,
Ed's post shows that low resistance and capacitive compensation in the divider is important for wide bandwidth.
Your 1M resistive dividers plus the input capacitance of the opamps and protection diodes will rolloff frequencies above only about 1kHz without having a compensation cap across each resistor in the divider. Maybe you should make a second divider with a 100K (1/2W total) resistance for looking at frequencies up to about 10kHz. ;D

[Guest Kasamiko]

Sure, your application is perfect for it.

Thanks for the assurance ;D

Are you going to look at the 240VAC output of inverters? ;D

No plan to TOAST my soundcard and PC.. :P
Maybe I can view the drivers waveform..
I'll try your probe..let see how it performs.. ;)

Thanks all

rhonn  ;) ;)