2022-02-15 05:25 AM
i want to convert 0-10V in to 0-3.3V linearly for analogue input of STM32 MCU so for this application any op-amp circuit which can done this?
Solved! Go to Solution.
2022-02-15 06:52 AM
It depends on what you want to do with the output voltage: should it be measured or is it used for further processing with an internal comparator or opamp?
If it is to be measured: does it necessarily have to be converted to 3.3V, or can you also accept a lower output voltage?
To stay with the measurement: both have advantages and disadvantages:
Let's assume for the sake of simplicity that you want to measure the signal converted from 10V to 3.3V. Then you can, for example, reduce the 10V to 3.3V with a voltage divider 67:10 (e.g. 68k+33k or a better optimized ratio), then buffer it with a Unity Gain Buffer Amplifier as described here in Wikipedia, fig 3, and then connect it to the ADC input.
If the opamp is supplied by VDD=3.3V, you have to make sure that it is a RRIO amplifier, i.e. rail-to-rail input and output, like e.g. TSZ121 or TZ181. Of course you can also use other types with a larger offset, but don't forget that the offset is an error in the output signal.
Good luck!
Regards
/Peter
2022-02-15 06:52 AM
It depends on what you want to do with the output voltage: should it be measured or is it used for further processing with an internal comparator or opamp?
If it is to be measured: does it necessarily have to be converted to 3.3V, or can you also accept a lower output voltage?
To stay with the measurement: both have advantages and disadvantages:
Let's assume for the sake of simplicity that you want to measure the signal converted from 10V to 3.3V. Then you can, for example, reduce the 10V to 3.3V with a voltage divider 67:10 (e.g. 68k+33k or a better optimized ratio), then buffer it with a Unity Gain Buffer Amplifier as described here in Wikipedia, fig 3, and then connect it to the ADC input.
If the opamp is supplied by VDD=3.3V, you have to make sure that it is a RRIO amplifier, i.e. rail-to-rail input and output, like e.g. TSZ121 or TZ181. Of course you can also use other types with a larger offset, but don't forget that the offset is an error in the output signal.
Good luck!
Regards
/Peter
2022-02-15 09:31 AM
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/Peter
2022-02-16 12:15 AM
Can you please suggest me any circuit schemetic for this.
Voltage divider > voltage follower for importance matching.
If I want to add protection here op voltage is must between 0-3.3V because more than 3.3V STM32 ADC pin demage how can I add this protection any circuit schemetic?
2022-02-16 12:50 AM
I had already made a circuit suggestion: a voltage divider that divides 10V to 3.3V (or smaller) and a voltage follower whose output is directly connected to the ADC input.
Does it answer your question?
Regards
/Peter
2022-02-16 02:06 AM
how can i protect ADC ip pin from over voltage >3.3V any suggestion with schematic?
2022-02-16 02:09 AM
If you use an operational amplifier supplied with 3.3V for the voltage follower, no higher voltage can occur at the ADC input.
2022-02-16 02:39 AM
op amp used for voltage follower circuit is rail to rail output right?
any other characteristic OP-AMP ic must have for this application ?
2022-02-16 02:50 AM
As I wrote earlier, the opamp must have both a rail-to-rail input and a rail-to-rail output because it operates as a follower with a gain of 1. That means that the output voltage is the same as the input voltage, but the output impedance is much lower.
Other requirements:
2022-02-16 04:08 AM
Thanks you so much now I got this.