I have an amplifier is designed to amplify the signal so that output is max. 2.5 V because my ADC can read only upto 0 - 2.5 V. But my circuit uses +5 and -5 V supply.
So I need a voltage limiter which can cut out output beyond that range.
I used a resistor with zener diode of 2.7V and 3.3V, but zener diodes are not sharp at such ranges.
Voltage divider at output doesn't work because I need only positive output.
Currently I am using 4 diodes to limit voltage upto 2.8V and in parallel with 1 diode in opposite direction to limit voltage upto -0.7 V.
Is there any better solution?
(I cannot change my supply voltage because of other components)
If your amplifier is an opamp:
1) Can you adjust the gain of the amplifier so that your signal is < 2.5V?
2) or can you reduce the input voltage so that the amplifier output is less?
I'm very surprised that the adc does not give a "do not exceed" input level.
Ya, I have set the gain of the opamp such that it amplifies the signal to 2.5 V. But since I am dealing with very small signal (EEG), sometimes noises are bigger than signal. In that case, the noises can go higher than 2.5 V.
I got the impression that you are using +/- 5 V supplies. The max "Main battery supply voltage" is 2.1 to 4.5 V. The min/max input is 0 to 1.0*Supply. See page 30 of the attached. OOPS, the "Manage Attachments" does not allow me to attach the datasheet. https://www.alldatasheet.com/datasheet-pdf/pdf/254805/TI/TPS65950.html
Sorry, that I did not described properly. I am using a board called gumstix, which has TSP65950 in it. So, it is internally powered by gumstix, which needs 5V supply.
I just have problem with my output connection to adc. I wanted to see if anybody could suggest me a simpler voltage limiter circuit. Right now I am using the diodes (in fig) which limilts voltage from -0.3 to +2.9 V