Op Amps Without Op Amps - Workbench Wednesdays 39

Maybe someday. I'm up to my ears with learning new platforms for another digital project. I don't have enough bandwidth for getting up-to-speed on yet-another-MCU.

I'm really starting to struggle with a good reason to stick to 8-bit MCUs anymore. The power management of modern Arm/32-bit MCUs is so good and their prices (when available.......) are usually lower than their 8-bit counterparts.

But, the AVR128DB is a really cool chip.

baldengineer  Will we be seeing more of the cool features of this chip?  I hope so.

Ouch. I know there are some other mixed-signal chips out there. Silego? I don't think this microcontroller is meant to compete there.

I really think this is a case where they had amplifiers for the DAC and ADC already and just extended the functionality a little bit.

Great demonstrations of the chip features.

At first I wanted to write that it seems like the competition is only slowly trying to catch up with Cypress PSoCs that also feature ADC, voltage / current DAC, op amps / comparators and analog multiplexors and most importantly a graphical IDE (PSoC Creator) that makes the development super easy - you can draw a schematics that is part of the project.

However, newer PSoC 6 is recommended to be developed on a multiplatform Eclipse-based IDE (Modus Toolbox) that lacks the graphical editor.

I would recommend against this method. Voltage dividers are lousy voltage sources, especially for a circuit like an op-amp.

As the current draw changes, the supply voltages are going to change. The result is going to be an unstable circuit. It might seem to work in a simulator, but it definitely will have problems in a real circuit application.

Hi!
An easier way to generate dual polarity supply from a single battery (of V volts) is to create a simple voltage divider network using two equal value resistors and making the junction of both resistors as ground. This way you can get +/- V/2.

Attached an image for reference. I'm using a 9V battery and 100 ohm resistors. However, as James suggested above, a simple inexpensive 9V battery won't be able to supply 100mA. You can try using a 9V lead acid battery or a Li-Po battery for larger currents.

Simulated using LTSpice.

Hi Wesley, if you need an output that swings below 0 volts, I could consider a charge pump.

If you can bias the input and output to stay positive. then I would use a LM358–or almost any other op amp than a ua741.

I am more concerned about you using a 9v battery! Those can barely supply 50 mA. They drop quite a bit even at 100 mA!

Very cool chip.

You did a good job of showing off some of its capabilities.

You could easily do a series of shows to really put the chip to some use cases.

DAB

James,

I never miss your videos, I think you do an excellent job presenting information.

With respect to an LM741 Op Amp, how would you build a circuit using a single power supply (i.e. a 9v battery) to supply the positive and negative supply rails?

Let's say the maximum current output might be around 100 mA.

Best regards,

Wes