# Attenuator calculation or formula

#### PickyBiker

Joined Aug 18, 2015
88
I have a microprocessor that is putting out 3.4V pulses and it needs to drive a sensor with a max input voltage of 2.4V

I think a T attenuator would work, but I don't know to calculate the values. Anyone got a calculator that works with voltage instead of db? A simple formula would be alright too.

#### wayneh

Joined Sep 9, 2010
17,168
There are more than one way to do this, but I might just use a resistive divider. What does the sensor require in terms of current, mA?

Another way could be as simple as putting 2 diodes in series with the signal. Together they will drop ~1.2-1.4V.

#### #12

Joined Nov 30, 2010
18,223
You don't need a T-attenuator. This is the basic shape of it considering I have no idea how much current the load needs.
Vo = Vin R2/(R1+R2)

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#### PickyBiker

Joined Aug 18, 2015
88
The current required to raise/lower the sensor input is 10ua.

#### #12

Joined Nov 30, 2010
18,223

#### wayneh

Joined Sep 9, 2010
17,168
The current required to raise/lower the sensor input is 10ua.
In that case, a resistive divider as I and #12 mentioned, and which #12 illustrated, would be fine. The 10µA load of the sensor would introduce only a small error (~1% max) in the 1mA flowing through the resistors. That error is likely dwarfed by other sources of experimental error.