Digital Analog Power Junction

Digital Interface to Analog Circuits is an example of Mixed Signal Design. Generating Digital Control Signals from the Analog sections in instruments is also done by Mixed Signal Circuit.

A/D Convertors and D/A Convertors are like Mixed Signal Chips. A Digital Potentiometer that controls an analog signal amplitude with a digital byte or word, figures in Mixed Design Circuit.

Analog Designs have to handle Linear Signals, Like 2.03 V and 35.3812 mA. Waveforms of all shapes from Straight Line DC Levels to the Jittery and Multi-Frequency Audio Waveforms.

Mixed Circuits Analog with Digital

350 MHz Mixed Signal Oscilloscope HMO3524 by HAMEG Instruments


Mixed Signal IC or ASIC are chips that are mainly Digital on the Core but have peripheral I/O within the chip to interface with the real world outside, over Analog Signals. Sensors and Actuators use signals in the analog language. The CPU with its Math Power, speaks Digital Words, its behavior thus can be patterned by a Software Program.

Fluid or Water Level with Reed Relays

Some Circuits on above pages are..

• Voltage to pulse converter using opamps
• Analog Section of 8751 based flowmeter
• Voltage to pulse converter impulse counter
• 16 channel analog multiplexer
• 8 channel analog mux with sample hold
• Digital Control for 8 channel analog mux

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Electrical Engineering encompasses Everything in Electronics. Communications, Computers etc. are further specializations of Electronics. So it is best to Identify Electrical Circuits with Electrical Designs which excludes Active Devices. It can include Electronic Products in the form of wireable modules.

• Electrical Control Panel Wiring
• Circuits using only  discrete devices
• Electronic Tables and Charts
• Mains Voltage and Power Circuits

So House and Factory wiring, Appliances like Ovens, Toasters, Power Generation and management; all these are electrical. Motors, Generators, Connectors, Relays, Contacters and Circuit Breakers are Electrical Components.

See a diagram i made for a Sequential Process Control Unit, custom built for Vacuum Impregnation;



A Radio or Power Inverter is Electronic. When an Inverter or Electronic AC-DC Motor Drive is used in a Control panel or Power Supply system, that integration is shown as an Electrical Circuit. I feel Simple Consumer Electronic Circuits using Diodes, Transistors, SCR, Capacitors and Resistors can also be taken under electrical circuits; when they are used in Mains-Power or Household Appliances. Solar Energy related circuits also can be studied under Electrical Power Circuits.

In Electronics RF-Microwave and Communications is a specialization area, Computer Hardware, Software, Internet form another major domain. Networking and Wireless data communication overlaps both the above.

Power Electronics and Instrumentation are fundamental domains needed for many. Industrial Automation with Process Control Instrumentation is unique, but is supported by the fundamental domains. Many more finer areas like Robotics and Medical Electronics have a much sharper focus.

Basic Electrical Circuits - delabs

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Analog devices like transistors and diodes lead to opamps and analog computing. This takes more parts but with fast devices can be real time. Then came Logic and Digital Circuits, here also big systems will take too many parts. A very Old hp Logic Analyzer instrument, could be HP1607A, had more than five large PCBs, Toggle Switches and numerous 74Fxx TTL Chips. I tried to revive it, it could not be fully restored.

Embedded Microcontroller - delabs

Then came the solution the Microprocessor. Here the entire system goes into the firmware and a Hardware Tool Set in the Microprocessor made up of Logic and Math is sequentially used to perform the same operation that would require innumerable Gates in a plain hardware digital circuit. But as it performs the operations one after another, it takes time and is defined by the CPU Clock Speed.



When the External RAM and EPROM and other peripheral devices moved into the main package, MicroController were born. When more external devices merged with the MicroController. It formed a nearly complete computer, this is known as the SOC.

• 80C51, SBC, Firmware and Circuits.
• Microcomputer Circuits in Process Control.
• Interface 80C51-80C31-89C51 to ICL7135.
• 80C39-8749 MCS-48 Examples and code.

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Mains Power means the 230 V AC 50 Hz or 110 V AC 60 Hz in some countries, The lower power line like 5A is used for small lamps and fans. The higher power line 15A is used to drive the High Power Electrical Appliances like Heaters and Motors. This is a single phase supply.

Mains Voltage and Power Circuits

Single phase Supply in layman language means a Live, a Neutral and an optional earth. The earthing is a must in every building along with lightning protection. The Neutral is a close to earth potential, The live can give a shock to a man who is in contact with earth at some part of the human body. So great care has to be taken. This live wire or point can be easily checked by a quality standards approved Neon Tester.



Three phase supply - there are three Live wires, used in factorys and apartments to power bigger loads and Motors. A 3 phase AC motor is very efficient and economical and most machines like Drills and Lathes are powered by AC Motors. 3 phase supply becomes essential for industry.

The voltage is transmitted and supplied to houses at a high level in comparison to low level of batteries. This High Voltage is not safe but Inevitable, as transmitting at lower voltage means greater current carrying requirements of wires and connectors. That leads to more copper or aluminum usage, more wastage of power due to I2R.

Earthing has to be good, use a Earth Leakage Trip Device. If earth wire gets snapped outside and some appliance is leaking, the metal clad appliances may give shock. Even if no appliance is leaking, the current thru y-capacitors of EMI Filters in Electronic Gadgets like computers are enough to make your Neon tester glow.

The Circuits related to Mains Power

• Stabilizer Step up 230V AC 500VA
• Solid-State Stabilizer Step up 110V AC
• Mains Voltage Current LED Indicators
• Simple Mains Voltage monitor LM324
• Mains Voltage monitor using LM3914
• Triac based Lamp Dimmer power control

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Operational Amplifiers - With a few Op-Amps and a regulated Power supply, many Instrumentation and Process control equipment can be designed. The Human Brain understands Numbers, Quantity and it regulation very well ! On the right you can see a analog controller based on opamps and discrete devices. A Heater, Fan and Motor is regulated, controlled and timed for a process.


Analog is about numbers, the circuits can be understood and designed mathematically or empirically. Designing and Building a True RMS Rectifier with Op-Amps, will help a designer digest many Op-Amp capabilities.

Analog Op-Amp Circuits

Things you ought to know about Op-Amps -

OpAmp part numbers from various semiconductor companies are designed for both General purpose and special applications. Some have to be cost-effective for consumer low-cost equipment, while others may be advanced in specs, closing in on an ideal Op-Amp.

• Square and Triangle Op-Amp Oscillator
• Inverting Amplifier - Op-Amp Circuits
• Non-Inverting Amplifier - Op-Amp Circuits
• Differential Amplifier - Op-Amp Circuits
• 3 Op-Amp Differential Instrumentation Amp
• Buffer or Unity Gain Op-Amp
• Two Op-Amp Differential Amplifier

Instrumentation opamps are used for accurate and low drift applications. These Op-Amps have stringent specifications and are used in the fields like Aerospace or Medical Electronics. A pre-amplifier for an FM Radio may need to be low-priced. Test Measurement needs Op-Amps which have near ideal specs in the area of measurement or application. CMOS low-power devices are used when designs are made for portable gadgets.

• Outputs cannot be Loaded beyond the drive capacities, Note Resistors and Output Load.
• Inputs draw a small bias current and will load the signal sources, compensate design.
• Op-Ams AF-RF or Switching performance study with Slew rate and Bandwidth.
• Power consumption of some Op-Amps are more and some very less, choose wisely.
• Look for Standard Pin-Outs, Price, Popularity and study Abs. Max, AC and DC Specs.
• Use Packages with multiple Op-Amps like LM324 to save board space and assembly time.
• Op-Amps and its 1% MFR resistors should have a separate supply and far from hot parts.
• Ultra Low Offset Voltage is required, when you wish to amplify a DC level of say 500uV.
• Guard rings to be used for High impedance inputs and EMI-RFI Shielding for AF Amplifiers.
• Glass epoxy PCB, clean surface, Pins and Tracks protected from Moisture and Chemicals.
• Avoid Ground Loops, Have regulated Low ripple Power supplies. Dynamic Isolation.

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