# Customizing both voltage and amperage in a circuit

I intend to control a motor via H-bridge L6205N (PowerDIP20). H-bridge's logic input requirements are:

• High level logic input voltage: 2-7 V

• High level logic input current: 10 μΑ

Motor's supply requirements are: 9 V, 0.4 A (approximately). Logic signals are the output of a BeagleBoard-xM (0.44 V). Thus, I have to customize signals to >2 V and <10 μΑ.

I thought of putting a 47 kΩ resistor, to customize amperage to 9.3 μΑ (via Ohm's law) and thereafter an non-inverting amplifier (close loop gain equal to 5) to customize voltage to 2.2 V.

Is my syllogism write and if not what is the way customizing both voltage and amperage? Is there something I have to pay attention for this circuit design?

• Logic current spec on the H-bridge controller inputs is not a requirement, it is a promise. If you supply between 2 and 7 V, the H-bridge controller promises not to take more than 10 uA. You should not have to change anything on the Beagleboard to make this happen, except for making sure the output is between 2 and 7 V. – The Photon Nov 12 '13 at 17:25
• electronics.stackexchange.com/questions/85450/… ; also, I think your output of BeagleBoard-xM at 0.44V sounds wrong – pjc50 Nov 12 '13 at 17:26
• (look for "logic level shifter" for changing the voltage of control signals) – pjc50 Nov 12 '13 at 17:30
• @pjc50 Normally, BB-xM's expansion ports generate 1.8 V signals. Mine, is a toggling line, which I measured 0.44 V. – dempap Nov 12 '13 at 17:34
• It will be 0.44V average, but it will swing between ~0V and ~1.8V. – Ignacio Vazquez-Abrams Nov 12 '13 at 17:34

## 1 Answer

You will need to shift the voltage level from 1V8 (BeagleBoard-xM) to 3V3 (2.31 Voh). The level shifter will have to put out a minimum of 10uA. Assuming you don't need ultra high speed, this can be done with a 74LVC07/07A with a 1V8 supply and 3V3 10kohm pullups on the outputs.

• Could a transistor as amplifier work in this case? – dempap Nov 13 '13 at 17:04
• @dempap: I'd use the transistor as a switch instead. It could work, but remember that some configurations using a single transistor will invert the signal. – Ignacio Vazquez-Abrams Nov 13 '13 at 17:47