# DC voltage amplification

Discussion in 'General Electronics Chat' started by hunterage2000, May 3, 2012.

1. ### hunterage2000 Thread Starter Senior Member

May 2, 2010
483
2
Hi,

Say you have a full-bridge circuit that is DC excited, what is the usual way of amplifying the bridge output? All I have ever seen in books is AC excitation and then amplified with op-amps. Is AC the most common way?

2. ### SgtWookie Expert

Jul 17, 2007
22,201
1,809
What do you mean by "amplifying" the voltage?

If you are speaking of voltage doubling/tripling/etc or boosting the voltage, it can be accomplished with DC using switched capacitors for low power applications, or switched inductors for higher power applications. That type of circuitry falls under the generic category of "Switch-mode power supply" or SMPS.

Note that if you boost the voltage, there is a corresponding loss in current; and on top of that you will have losses due to inefficiencies in the circuit itself. Power out will always be less than the power in. There is no "free lunch" in electronics.

If your input supply is capable of delivering 10v at up to 1A, and you have a circuit that will boost the 10v to 20v, then your maximum output current will be less than 500mA (0.5A).

3. ### hunterage2000 Thread Starter Senior Member

May 2, 2010
483
2
If I used DC excitation for a full-bridge circuit using strain gauges, I would get small bridge outputs of mVolts so I imagine I would need to boost it to Volts. The voltage would then be converted to a linear 4mA to 20mA output.

4. ### #12 Expert

Nov 30, 2010
18,076
9,691
You are on the right track. Your question was confusing in that a "full wave bridge" is a very common circuit and we didn't know if that was your point of interest.

DC is the most usual way to excite a Wheatstone bridge circuit.

Oct 2, 2009
19,129
6,148
6. ### hunterage2000 Thread Starter Senior Member

May 2, 2010
483
2
I have a good howland current source from a book that I will use, I just need a few ideas for the circuitry between the bridge and the howland.