Can I adjust the volume of a DAC using PWM?

Here is a circuit that allegedly converts PWM into a precision voltage reference: (source: I am thinking about feeding that reference into the reference line on this MCP4921 DAC. My goal is to generate waveforms that use the entire range I need (0-2v) and be able to digitally adjust the volume or max output … Read more

“LB” component reference designator

I’m doing a bit of reverse engineering on my Das Keyboard Model S Ultimate. I’m beginning to develop a pretty good understanding of the circuitry, but I am confused about one type of component on the board. There are 4-5 components on this board with the reference designator of LB. This isn’t a standard refdes … Read more

Versatile input termination / translation for reference clock?

I’ve got a microcontroller I want to clock from an external 10 MHz reference. I’d like the reference input to be as versatile as possible. At the moment, my reference is an LVCMOS square wave, but other folks have various levels of sine wave references. I’m going to use a 74LVC1G17 to condition the input, … Read more

AREF Voltage same as VDD but through a reference IC

My project has 9V and 3.3V on the board. I would like to use a precision voltage reference IC for the analog reference on the MCU (MCU powered by 3.3V). The precision of the voltage reference IC is 0.5%, which is more precise than the 3.3V regulated output voltage from the regulator powering the MCU. … Read more

Series voltage reference output voltage

What is output voltage of series voltage reference IC (for example MAX6100) when input voltage is below minimum input voltage? Is it zero volts, or something else? Didn’t find answer to this from data sheets I was reading. Thanks. Answer If you can’t find the answer in the data sheet then you can’t make any … Read more

Reference manual & Datasheet

I am new in the world of microcontrollers and I want to know the main differences between a Datasheet and a Reference Manual of a microcontroller and when do I use one and when the other. Answer The datasheet for a microcontroller generaly covers the specific details about a single chip, or a closely-related group … Read more

Driving 18 Thermistors in parallel

I am designing a circuit that needs to have 18 thermistors to measure the temperature at various points. The thermistors are 2metres+ away from the ADC Usually when I power a thermistors I use a Vref IC and an opamp buffer. I also take the op-amp buffer into the ADC ref for ratiometric measurement. With … Read more

Problems solving strategies of experts in simple DC-circuit problems

There are many papers which study how students in high school and college think, when solving elementary DC-circuit problems. However I don’t know any resources where the reasoning of experts is described in detail when solving such problems. I am only interested in qualitative (circuits with batteries and light bulbs)- problems. Consider for example the … Read more

Measure resistance accurately with an arduino?

I’m looking at performing accurate temperature measurements with a three wire RTD, and I’d like to be able to measure the resistance and thus the temperature using an arduino. The accuracy I’m looking for is better than 0.1Ω @ 100Ω. I was told that to get good accuracy, I would first need a stable accurate … Read more

Using 2 terminal band gap voltage reference

Specifically, LM385. Am I correct in assuming that a resistor is chosen to pass a current between 50uA to 10mA through the device from the PSU, and the reference voltage appears across the terminals? Answer You assume correctly – you decide on the voltage regulation point (volts), subtract that from your power supply voltage and … Read more