This tutorial discusses some general rules of thumb that make it easy to understand and analyze the operation of most opamp circuits. It presents some ideal properties of opamps, and discusses how negative feedback generally causes the input voltage difference to be equal to zero (input voltages are made equal by the action of negative feedback). In other words, the output will do whatever it can to make the input voltages equal. Applying this simple fact makes it easy to analyze most opamp circuits.
Basics of Opamp circuits – a tutorial on how to understand most opamp circuits - [Link]
Super cheap way to make a dummy load for testing high power PSUs.
Dummy load in a bucket - [Link]
The ring counter is useful in hardware logic design such as Application-Specific Integrated Circuit (ASIC) and Field-Programmable Gate Array (FPGA). The ring counter is also ideal in creating simple finite state machines.
The diagram is a circuit of a 4-bit twisted ring counter which can function in 4 different modes, namely: Serial-Input-Serial-Output (SISO), Serial-Input-Parallel-Output (SIPO), Parallel-Input-Serial-Output (PISO), and Parallel-Input-Parallel-Output, by applying Qo to the serial input, the resulting circuit will be a twisted ring or a Johnson Counter. Twisted ring counters are shift registers where the output from the last flip-flop becomes the input of the first flip-flop; it will result in a closed loop circuit which recirculates the data bits around a continuous loop for every sequence state.
The circuit is composed of NAND gates, flip-flops, voltage sources, and clocking system. The NAND gates are incorporated in a Quad-2 input NAND Gate integrated circuit with part number 74ABT00D. The NAND gates receive the inputs from D0, D1, D2, and D3. This device is fully specified for partial power down applications using IOFF. The IOFF circuitry disables the output, preventing the potentially damaging backflow current through the device when it is powered down. The circuit also uses JK flip flops as the memory element. For this circuit, the dual JK flip-flop IC with part number 74HC109D is used. Two 74HC109D chips are used since the circuit needs four JK flip-flops and each IC has two JK flip-flops in it. The 74HC109 is a dual positive-edge triggered, JK flip-flops with individual J, K inputs, clock (CP) inputs, set (SD) and reset (RD) inputs; also complementary Q and Q outputs. The set and reset are asynchronous active LOW inputs and operate independently of the clock input. The supply voltages used to power the ICs are set at 5V for 74ABT00D IC and -1.5V for the 74ABT00D IC. The clocking system connected to the flip-flops provide synchronization pulses and timing for the circuit.
- 74ABT00D Quad-2 input NAND Gate
- 74HC109D Dual Positive-edge triggered JK flip-flops
- Clocking system
- +5V DC Voltage Source
- -1.5V DC Voltage Source
4-bit Twisted Ring Counter using JK Flip Flops – [Link]
Here is a simple 555 timer circuit that lights a LED when dark is detected on LDR. Components used are wide available.
In this episode Shahriar continues his investigation of discrete Bipolar amplifier design. The advantages and disadvantages of Class-A amplifiers are explained. The conceptual schematic of a Class-B amplifier is presented which leads to the introduction of Class-AB amplifier circuit to overcome the ‘dead-zone’ impairment of a push-pull Class-B design. To further improve the Class-AB amplifier and lower its input impedance, a final Class-A followed by Class-AB amplifier is presented The component parameters are calculated and the schematics is explained in detail. All circuits are then implemented on a breadboard and tested both in the time domain and frequency domain. All schematics can be downloaded from The Signal Path website.
Tutorial on the Design and Characterization of Class-B and AB Amplifiers - [Link]
Anthony Smith writes:
Low-current, momentary action pushbutton switches, such as PCB-mount ‘tactile’ types, are cheap, and available in an abundance of different styles. Latching types, on the other hand, are often larger, more expensive, and available only in a relatively limited range of styles. This can be a problem if you need a small, inexpensive switch for latching power to a load. The solution is to convert a pushbutton’s momentary action into a latching function.
Latching power switch uses momentary pushbutton - [Link]
amandaghassaei @ instructables.com writes:
The Arduino is a pocket-sized computer (also called a “microcontroller”) that you can program and use to control circuits. It interacts with the outside word through sensors, leds, motors, speakers… even the internet; this makes it a flexible platform for lots of creative projects. Some popular uses include:
- programmable light displays that respond to music or human interaction
- robots that use information from sensors to navigate or perform other tasks
- unique, customizable controllers and interfaces for music, gaming, and more
- connecting real world objects to the internet (twitter is especially popular)
- anything interactive
- automating and prototyping
Beginner Arduino Course - [Link]
This is a simple 3.3V and 5V dual power supply using LD1117V50 and LD1117V33 low dropout voltage regulators.
I normally use a USB port as power supply for my projects but some ICs need 3.3V instead of 5V. Therefore I decided to build this small dual power supply. Power supply uses two low dropout voltage regulators that provide up to 800mA of output current and come in TO-220 package. LD1117V33 is used for 3.3V and LD1117V50 for 5V. Input voltage is 6V-15V and both regulators can be switched on/off individually.
3.3V and 5V Power Supply - [Link]
Here is an app note from NXP on capacitor bypassing.
Bypass capacitors are applied between the power supply pins VCC and GND of integrated circuits. They reduce both the power supply noise and the effect of spikes on the supply line. They also provide instantaneous current demands of the integrated circuit as it switches. This application note describes the different properties of bypass capacitors and provides a guide to their use.
Properties and application of bypass capacitors - [Link]