Hello,
I want to convert PWM of Arduino to a 12 or 14-bit bipolar signal (+/- 5V).
Based on my research, I do have two options:
using an Opamp
using a H-bridge
Besides the cost, what are the big differences between these options?
As aside note, I believe for both I might use a DAC to convert to 12 or 14-bit resolution (some Opamp might already have a built-in DAC, so I might not need to use a DAC but for H-bridge I need to use one, I guess).
Thanks,
What's this for? How much current?
The regular Arduino PWM is 8-bits.
An H-bridge can "reverse" the connections. So for example, you can reverse a motor by putting 5V across it one way then 5V the other way, effectively supplying +5 or -5V (as long as the motor has no ground connection). It doesn't (normally) go negative relative to ground.
An op-amp can go negative relative to ground as long as it has a negative power supply.
As aside note, I believe for both I might use a DAC to convert to 12 or 14-bit resolution
An H-bridge isn't analog and PWM isn't analog. (And op-amp can work either way.)
some Opamp might already have a built-in DAC
No, but there are specialty audio chips with a DAC and an amplifier and probably other specialty chips with both.
Thanks for your reply.
It is for an actuator that needs to be driven by a sine wave. The maximum current can go up to 500mA.
The resolution of PWM (I guess 8 bit) is not enough for me so I need to use a DAC to improve that (right?).
What is the problem using a 12 or 14 bit DAC in series with an H-bridge (might be a crazy question)?
If I need to use an Opamp, any suggestion?
Thanks again
It is for an actuator that needs to be driven by a sine wave. The maximum current can go up to 500mA.
That's too much current for a "normal" op-amp.*
The resolution of PWM (I guess 8 bit) is not enough for me so I need to use a DAC to improve that (right?).
I have no idea if that's enough resolution for your application but I'd be surprised if the actuator is that "precise".
What is the problem using a 12 or 14 bit DAC in series with an H-bridge (might be a crazy question)?
A standard H-bridge* is not analog. 
It has 3 states... Direction/polarity-1, Direction/polarity-2, and off. With PWM you can adjust the average voltage (and/or current & power). Note that your PWM frequency needs to be much higher than your "sine-wave" frequency.
eydad:
It is for an actuator that needs to be driven by a sine wave. The maximum current can go up to 500mA.
Please provide full details of all the hardware you are talking about, details always matter - what actuator? Where is its datasheet?
Are you saying that I need to put H-bridge between the Arduino and the amplifier?
Not sure if I understood it correctly. I found an audio amplifier PAM8610:
It has enough power.
Thanks,
You have been asked to provide full details of the hardware.
The PAM series of amplifiers are class-D, which means digital/switching amplifiers.
Almost the same as a digital H-bridge if you use them in bridge mode.
A tiny one, like the PAM8403, powered by 5volt, can already produce (almost) 10volt peak/peak.
But your hardware might not like a digital signal, meant for a speaker/inductor.
Leo..
eydad:
- You might be able to use an audio power amplifier in a bridge configuration (or as a regular bipolar amplifier with dual power supplies). A 10V peak-to-peak sine wave is about 3V RMS and 3V x 500mA is 1.5 Watts. So, you'd need an amp rated at 1.5W or more. Almost all audio power amps have some voltage gain so you'd a pot/attenuator on the input.
Are you saying that I need to put H-bridge between the Arduino and the amplifier?
No. Just use the amplifier, feed it analog via a DAC.
What is your actuator exactly please? Until you answer this we may be missing a trick.
MarkT:
No. Just use the amplifier, feed it analog via a DAC.What is your actuator exactly please? Until you answer this we may be missing a trick.
I did not have the datasheet but I found one which is very close to what I am using:
Two parts may look the same, have the same function, but be controlled very differently. Unless you can give the details of YOUR specific part - preferably in the form of a manufacturer's data sheet - it's still guesswork.
The page you shows doesn't say anything about current or sine wave or whatever, yet you know those details. Where did you find that information about your part?