Circuits & Schematics Supply

The circuit in Figure 1 serves as a variable, current-sink load for testing voltage sources. You use digital commands to set the load current of the device under test over a wide range, independently of the device under test's output voltage. ...

The circuit in Figure 1 derives its power from a USB port and produces 5 and 3.3 V supply rails for portable devices, such as digital cameras, MP3 players, and PDAs. The circuit allows the port to maintain communications while, for example, ...

This Design Idea describes an enhancement to a previous one ( Reference 1 ). The circuit in Figure 1 uses a normally open SPST pushbutton switch, S 1 , instead of the SPDT switch that the original design required. You can use a membrane switch to ...

I recently needed to control nine seven-segment displays for a microcontroller's serial port. The complication I faced was the need to provide a continuous brightness adjustment for all the digits from completely dark to fully bright. I ...

In dc/dc-converter applications in which the input voltage may be lower or higher than the output voltage, you can use either a flyback converter or a SEPIC (single-ended-primary-inductor converter). SEPICs offer lower input-current ripple and ...

It is always desirable to use a low-battery indicator that consumes as little power as possible. For a 9 V, 450-mAhr alkaline battery, a 50-µA low-battery indicator can by itself run the battery down in a little more than a year. ...

The reflex, or “red-dot,” sight is a popular category of optical aiming/pointing aids, which finds diverse applications in astronomy, archery, shooting, etc. In the reflex-style sight, a source typically a high-intensity LED is ...

The original bipolar 555 timer, the NE555 , is excellent for driving a power MOSFET’s gate. Newer CMOS versions such as the 7555, LMC555, and TLC555 use less power, but they have trouble sourcing enough current to drive a gate well and can ...

The LM324 is a cost-effective choice for an op amp, especially when you need to apply ground-level inputs. Although its output purportedly includes ground, its poor current-sinking capability limits the applications. At output voltages lower than ...

You sometimes need to drive a white LED from one 1.5 V battery. Unfortunately, the forward voltage of a white LED is 3 to 4 V. So, you would need a dc/dc converter to drive the LED from one battery. Using the simple circuit in Figure 1, you can ...