I want to build an electronic circuit

[Witain]

I want to build an electronic circuit to convert an NTC 10 kiloohm (B=3950) signal into an output voltage that can supply 2-3 amps. The output voltage should correspond to the measured temperature (4V at 25°C to 12V at 50°C), i.e. have a range of 4V to 12V DC. Is this typically done with a buck/boost converter and a coil and capacitor? Or is there a ready-made chip that I can use to achieve a maximum output voltage of 12V DC? The power supply comes from a PC power supply (12V DC). The purpose of the circuit is to control the speed of one or more DC fans using a changing operating voltage at the fan, without using PWM. To linearize the NTC and process the voltage, I was thinking of using a TLV9002 from TI. Can anyone help me with the rest of the circuit? No programming, no software, no Arduino, no PLSOC, just more or less classical built up with only a few compenents.  Is that possible?

[HarryA]

 The TLV9002 output at 25C is 67.8 mv; to get 4v one would need an amplifier gain of 58.99

At 50C the output is 3.27v ; to get 12 volts one would a gain of 3.66

I think a log amplifier would work here.

"Log amps are non-linear, analog amplifiers that produce an output that is the logarithm of the input signal or the signal’s envelope. They compress input signals having a large dynamic range into output signals with a fixed amplitude range. This is accomplished by providing high gain for low input signal levels and progressively lower gain for higher level signals"

The LTspice simulator has one Analog Devices log amplifier in it. I could try to simulator a circuit using a ramp of 67.8mv to 3.27  As Analog Devices has numerous log amplifier chips and they own the the LTspice simulator it seems odd there would not be more.

 

[Steven Ramos]

Can you give me a call?

[ilianaboone]

Yes, it's definitely possible to create a circuit to convert the NTC thermistor's resistance into a corresponding output voltage that drives a DC fan without relying on PWM, and without using microcontrollers or complex software.