Logarithmic Compressor and Decompressor circuits
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Please see recent upload…
I started from basics. to create a simple log compressor for a limited range of input. That seems to work well in an "ideal" simulation, using Univ OpAmp2. Then I got inspired to test an equally simple DEcompressor by putting the circuit in the feedback path of another UniOpAmp2, which also worked (surprisingly) well.
Replacing the amps in the Compressor path with LT1012's appears to work just as desired, as well. But replacing the DEcompressor amps fails miserably.
What can I learn today?
Dave |
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Not to use costly LT1012s? Bur seriously, what
happens if you put another real opamp as U3 and U4. I can't
check, because I can't see how to change from the Uopamp2 to a
real one. Do I have to delete the symbol from the schematic and
put in a new one? I've never used Uopamp2. On 2024-11-10 21:38, Bell, Dave via
groups.io wrote:
-- OOO - Own Opinions Only Best Wishes John Woodgate Keep trying |
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Yes, delete and replace. I haven’t tried other LT opamps yet, either
From: LTspice@groups.io <LTspice@groups.io>
On Behalf Of John Woodgate
Sent: Sunday, November 10, 2024 2:52 PM To: LTspice@groups.io Subject: EXTERNAL: Re: [LTspice] Logarithmic Compressor and Decompressor circuits
Not to use costly LT1012s? Bur seriously, what happens if you put another real opamp as U3 and U4. I can't check, because I can't see how to change from the Uopamp2 to a real one. Do I have to delete the symbol from the schematic and put in a new one? I've never used Uopamp2. On 2024-11-10 21:38, Bell, Dave via groups.io wrote:
-- OOO - Own Opinions Only Best Wishes John Woodgate Keep trying
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I just tried LT1022’s for U3/4, and they work fine. Weird?
From: LTspice@groups.io <LTspice@groups.io>
On Behalf Of Bell, Dave via groups.io
Sent: Sunday, November 10, 2024 4:07 PM To: LTspice@groups.io Subject: EXTERNAL: Re: [LTspice] Logarithmic Compressor and Decompressor circuits
Yes, delete and replace. I haven’t tried other LT opamps yet, either
From:
LTspice@groups.io <LTspice@groups.io>
On Behalf Of John Woodgate
Not to use costly LT1012s? Bur seriously, what happens if you put another real opamp as U3 and U4. I can't check, because I can't see how to change from the Uopamp2 to a real one. Do I have to delete the symbol from the schematic and put in a new one? I've never used Uopamp2. On 2024-11-10 21:38, Bell, Dave via groups.io wrote:
-- OOO - Own Opinions Only Best Wishes John Woodgate Keep trying
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Never mind; LT1022’s don’t work
From: LTspice@groups.io <LTspice@groups.io>
On Behalf Of Bell, Dave via groups.io
Sent: Sunday, November 10, 2024 4:10 PM To: LTspice@groups.io Subject: EXTERNAL: Re: [LTspice] Logarithmic Compressor and Decompressor circuits
I just tried LT1022’s for U3/4, and they work fine. Weird?
From:
LTspice@groups.io <LTspice@groups.io>
On Behalf Of Bell, Dave via groups.io
Yes, delete and replace. I haven’t tried other LT opamps yet, either
From:
LTspice@groups.io <LTspice@groups.io>
On Behalf Of John Woodgate
Not to use costly LT1012s? Bur seriously, what happens if you put another real opamp as U3 and U4. I can't check, because I can't see how to change from the Uopamp2 to a real one. Do I have to delete the symbol from the schematic and put in a new one? I've never used Uopamp2. On 2024-11-10 21:38, Bell, Dave via groups.io wrote:
-- OOO - Own Opinions Only Best Wishes John Woodgate Keep trying
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Well, LT1037’s work in U3/4. But NOT as U1/2 (oscillate wildky)
From: LTspice@groups.io <LTspice@groups.io>
On Behalf Of Bell, Dave via groups.io
Sent: Sunday, November 10, 2024 4:14 PM To: LTspice@groups.io Subject: EXTERNAL: Re: [LTspice] Logarithmic Compressor and Decompressor circuits
Never mind; LT1022’s don’t work
From:
LTspice@groups.io <LTspice@groups.io>
On Behalf Of Bell, Dave via groups.io
I just tried LT1022’s for U3/4, and they work fine. Weird?
From:
LTspice@groups.io <LTspice@groups.io>
On Behalf Of Bell, Dave via groups.io
Yes, delete and replace. I haven’t tried other LT opamps yet, either
From:
LTspice@groups.io <LTspice@groups.io>
On Behalf Of John Woodgate
Not to use costly LT1012s? Bur seriously, what happens if you put another real opamp as U3 and U4. I can't check, because I can't see how to change from the Uopamp2 to a real one. Do I have to delete the symbol from the schematic and put in a new one? I've never used Uopamp2. On 2024-11-10 21:38, Bell, Dave via groups.io wrote:
-- OOO - Own Opinions Only Best Wishes John Woodgate Keep trying
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The LT1037 is not unity-gain stable - needs to be for the logamp.
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-- Regards,
Tony On 11/11/2024 01:20, Bell, Dave via
groups.io wrote:
Well, LT1037’s work in U3/4. But NOT as U1/2 (oscillate wildky) |
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I admit, I hadn't looked at Dave's circuit yet. But I've been there
before.
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-- Regards,
Tony On 11/11/2024 15:08, Andy I via
groups.io wrote:
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I know… The decompression was a side thought; the simple log conversion was what I intended for use in an embedded data acquisition application. Low frequencies, constrained input ranges, but wider than a uC ADC can adequately fit over maybe 3 decades. With compression, I can get good (enough) resolution at the low end and a single input range. Could use a little temp compensation, but otherwise all I need.
Dave
From: LTspice@groups.io <LTspice@groups.io> On Behalf Of
Andy I via groups.io
Sent: Monday, November 11, 2024 6:09 AM To: LTspice@groups.io Subject: EXTERNAL: Re: [LTspice] Logarithmic Compressor and Decompressor circuits
But first, you need to start with getting the polarities right!
Then worry about excess phase and unity-gain stability. Those are secondary.
Andy
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Bell, Dave
John Woodgate
Tony Casey