I have a joystick that puts out analog voltage somewhere between 1.5V and 3.5V.
I want to transform this range of voltage to control a motor controller that takes analog voltage between 0V and 5V.
How do I level shift and amplify properly?
Electronic – Analog voltage level conversion (level shift)
analoglevel-shiftingoperational-amplifiervoltage
Related Solutions
We are using the 4-channel bidirectional TXS0104E in a commercial product, and it is working very well for us.
In our case it is being used to convert from 3.3v to 1.8v and vice versa, but it can also be used to convert from 5v to 3.3v and vice versa (actually the high side can be anywhere from 2.3v to 5.5v, and the low side from 1.65v to 3.6v).
The chip also includes ESD protection on all pins.
It is available from Digi-Key in a 14-TSSOP package for $1.87 in single quantities (73 cents in 1000's). It is also available in an itsy-bitsy (1.9 x 1.4 mm) 12-DSBGA package. That's about the same size as an 0805 resistor. So you can easily fit them inline on top of a parallel bus going between chips. The pins are nicely arranged in order on both sides of the chip to accommodate this.
simulate this circuit – Schematic created using CircuitLab
The LM358, being a single supply op amp, saturates in the negative direction within a few mVs of the negative supply rail.
Best Answer
You want a simple gain of 5/2 = 2.5 centered around 2.5 V. This is easy assuming you have 5 V power available, like from the motor controller:
This needs to be a rail to rail output opamp that can run from 5 V power, like the MCP6041 and many others. R1 and R2 form a voltage divider to make the 2.5 V around which the input signal will be amplified. C2 attenuates noise from the 5V supply even more than the DC to make a quiet and smooth DC level. The opamp is in a classic positive gain configuration, with R4 and R3 setting the gain. The impedance of the 2.5 V source produced by R1 and R2 effectively add to R3 for the purposes of gain, but that is a small contribution of 1.2 kΩ on 100 kΩ. The gain will be slightly less than 2.5.