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Low volt noise gen

J

John Larkin

Jan 1, 1970
0
Is the hiss originating from the LM386 chips or from some
other component? Phil's data shows the result of a test of
the LM386 generated noise.

He did specify that the input pins were grounded. In real life, simple
chips like this tend to run the input stage at high currents, which
skews things towards low voltage noise and high current noise. So if
the input were driven from a reasonable non-zero impedance, or just
left open, there would be a bunch more noise.

Amplifiers with grounded input pins tend to have a bad s/n ratio,
especially if you measure it in dB.

I wonder what's the absolutely worst noisy amplifier thing around. I
recall seeing opamps that ran over 100 nv/rthz somewhere.

John
 
J

john jardine

Jan 1, 1970
0
[...]
I wonder what's the absolutely worst noisy amplifier thing around. I
recall seeing opamps that ran over 100 nv/rthz somewhere.

John
National's LMC6044, cheap, low power, CMOS quad opamp is getting pretty
close with an excruciating 83nV at 1kHz. Was my second user experience with
these new fangled device. First time round was the totally rubbish LM660.
Now, I just love the more recent CMOS opamps!.
 
J

John Larkin

Jan 1, 1970
0
[...]
I wonder what's the absolutely worst noisy amplifier thing around. I
recall seeing opamps that ran over 100 nv/rthz somewhere.

John
National's LMC6044, cheap, low power, CMOS quad opamp is getting pretty
close with an excruciating 83nV at 1kHz. Was my second user experience with
these new fangled device. First time round was the totally rubbish LM660.
Now, I just love the more recent CMOS opamps!.

Cool. Using all four stages, with the first as the noise gen, you
could get all the noise you could ever want. Maybe sum the first two
as the generators and use the other two as amps, for slightly better
statistics.

The old MF10 switched-cap filter was awful. PSRR was also nil, or
maybe worse than nil.

John
 
P

Phil Hobbs

Jan 1, 1970
0
John said:
[...]
I wonder what's the absolutely worst noisy amplifier thing around. I
recall seeing opamps that ran over 100 nv/rthz somewhere.

John
National's LMC6044, cheap, low power, CMOS quad opamp is getting pretty
close with an excruciating 83nV at 1kHz. Was my second user experience with
these new fangled device. First time round was the totally rubbish LM660.
Now, I just love the more recent CMOS opamps!.

Cool. Using all four stages, with the first as the noise gen, you
could get all the noise you could ever want. Maybe sum the first two
as the generators and use the other two as amps, for slightly better
statistics.

The old MF10 switched-cap filter was awful. PSRR was also nil, or
maybe worse than nil.

John
So was the LM359 "improved" Norton amp that they did all those active
filter app notes on. Horrible. The LMF100 is much much better than the
MF10.

Cheers,

Phil Hobbs
 
M

Mike Monett

Jan 1, 1970
0
john jardine said:
National's LMC6044, cheap, low power, CMOS quad opamp is getting
pretty close with an excruciating 83nV at 1kHz. Was my second user
experience with these new fangled device. First time round was the
totally rubbish LM660. Now, I just love the more recent CMOS opamps!.

John, I can't find a datasheet for the LM660, but I was interested in using
the LMC662 which may be similar. Besides the 22nv/rootHz noise, is there
anything else that causes you to dislike the part?

Regards,

Mike Monett
 
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