Rich D.
Active Member
This should be simple really. I was drawing up a temperature sensor with an analog output to a 0-5 Vdc ADC input to a microprocessor. This circuit doesn't need a lot of precision or accuracy, just a relative measurement for the user to view.
A cheap NPN is to be used. The Vbe changes inversely with the temperature. It's a small change, maybe less than 50-ish mV over typical room temperature ranges - not a lot of resolution for an ADC input. For improved resolution, I was going to rewire an OpAmp for gain and I would have to deal with it's issues. But then I thought: If I could connect several transistors in series, if each one changes 50 mV, then 4 of them would change 200 mV.
Does anybody see anything wrong with this idea or was this a flash of brilliance on my part?
A cheap NPN is to be used. The Vbe changes inversely with the temperature. It's a small change, maybe less than 50-ish mV over typical room temperature ranges - not a lot of resolution for an ADC input. For improved resolution, I was going to rewire an OpAmp for gain and I would have to deal with it's issues. But then I thought: If I could connect several transistors in series, if each one changes 50 mV, then 4 of them would change 200 mV.
Does anybody see anything wrong with this idea or was this a flash of brilliance on my part?