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Part Number: TL026
The customer is using TL026. The VCC+ pin(6 pin) is 12V. The VCC pin (3 pin) is GND.
Now the customer cannot provide the schematic for me. Once he provides the schematic for me, I will upload.
His design is like this:
(1) . A 6V bias voltage are input to both the IN+ pin and the IN- pin. And Another 200KHZ,30mVpp sine wave is input to the IN- pin at the same time.
(2). Then the customer tests the REF OUT pin voltage. It is about 7.31V. And this voltage remains the same.
(3). After the customer inputs the different voltage values to the AGC pin, then he tests the OUT- pin voltage. Please check the below informatio:
The AGC pin voltage value The Vpeak voltage of the OUT- pin
7.26V~7.428V FROM 668mV TO 38.8mV
7.452V~7.637V FROM 51mV TO 207mV
7.6387V~7.855V FROM 207mV TO 68mV
>7.855V , the voltage waveform of the OUT- pin is messy.
Q1: When the VCC+ pin(6 pin) is 12V. The VCC pin (3 pin) is GND, what is the voltage range for the REF OUT pin? Is 7.31V OK?
Q2: What is the voltage range for the AGC pin?
Q3: As the datasheet description, when the AGC pin voltage is less the REF OUT pin voltage 180mV, the gain is the max value.
When the AGC pin voltage is higher than the REF OUT pin voltage 180mV, the gain is the min value. Is my understanding correct?
If my understanding is correct, for the customer's issues, why does the voltage of the OUT- pin increase first, then it reduce?
This is not consistent with the datasheet.
Q4: The customer would like to control AGC pin voltage to determine the gain. Is this idea correct?
Best Wishes, Mickey Zhang Asia Customer Support Center Texas Instruments
Regards,Ronald MichallickLinear Applications
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In reply to Ron Michallick:
The AGC function works in a controlled manner when the output difference is used, [OUT+] - [OUT-].
This is gain vs. VAGC - VREF
Here is the gain using the output as single ended.
At low AGC voltage, OUT+ has twice the gain of VOUT-
The VOUT- gain is not monotonic , but VOUT+ is monotonic.
At high AGC voltage, both outputs are opposite phase and equal.
The OUT+ signal by itself may (or may not) work for your application.
For best performance both outputs should be used.
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