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Amnd • Apr 18, 2012

Need Help on Using FET as a Switch

To explain the kind of switching I'm trying to achieve, let me give a background story first 😁 I'm currently working on a project of making a carbon monoxide concentration meter using an MQ-7 sensor. This particular sensor needs a unique kind of voltage for its inner heater circuit: it needs a periodic voltage with 60 seconds of 5 V, and 90 seconds of 1.4 V, then repeat.

I plan on using a microcontroller to control the voltage given to the FET in line with the periodic pattern explained above. At first I planned on using a BJT as the voltage switch but my lecturer suggested on using FET instead.

An article on using FET as a switch that I understood most was this: However, that article and the other ones I read only explained how to switch between a voltage and 0 voltage, so I'm a bit unsure as to how to switch between two different voltages instead (5V and 1.4 V). Is there a way of achieving this using a similar circuit?

Thank you in advance 😀
Harshad Italiya
Harshad Italiya • Apr 18, 2012
You are able to get such switching using BJT? Get 1.4V instead of 0V using one BJT is difficult. Although I will check about it.

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