It's not a matter of acceptance.
It's performing that function reasonably well with just a couple transistors.

What is the exact input voltage range you have for a 0V to 3.5V output?

Well, I only know that hall effect output voltage from 3.736V (step up) to 0.802V (step down) to the ECU, so I think it is the exact input voltage to the circuit you design.

Of course, ideally the output voltage from the circuit is 0.802V to 3.736V, I want to limit the 3.736V down to 3.0V but not sure yet because I don't know how fast the ECU will drive the motor at 3.0V input.

Best regards,

Kelvin.

 

Okay, here's a single transistor quick and dirty circuit that will likely be frowned upon by many but it's simple.
The circuit operation uses the value of transistor current gain (Beta) for its operation and is thus significantly affected by the gain of the particular transistor you use (since the gain can typically vary by a a 3:1 range unit-to-unit).
This means you will have to tweak the 250k Ω pot U1 and possibly the value of R1 to get the desired transfer function.
The circuit is also sensitive to ambient temperature so, if that varies significantly, the circuit may not perform satisfactorily for your application.

View attachment 184888

Million thanks, crutschow. As a student project, it is very nice and good enough to have a quick and dirty circuit to let the student experience the concept and finish the prototype with limited resource, of course, as a product, we must deeply consider many matters.

I will try this circuit and come back to you later, thanks again.

 

Here's the circuit modified so the output goes from 0.8V to 3V.
The added emitter resistor determines the minimum output voltage.

 

Here's the circuit modified so the output goes from 0.8V to 3V.
The added emitter resistor determines the minimum output voltage.

View attachment 184905

Thanks crutschow, I tested with your circuit and it works perfectly. Here is the result I measured. I connect the circuit Vcc and GND to the ECU, the ECU mainly provides power to the circuit and pedal. I tune the resistance Rtot-250K to around 100k and the voltage output from the circuit is around 0.8V, this is the expected voltage level.

Below record is the output voltage from the circuit when I disconnect and connect the output to ECU (signal pin)

I try to change the Rtot-250K, although I can increase the voltage output from the circuit, the voltage will also be increased when the pedal release. Now I have to fix the min voltage output at 0.8V but want to widen the range, may I know which component I should change and widen the output voltage range?

I would appreciate if you could give me some more instruction.