Tag Archives: OPAMP

Passive Infrared Detector Circuit

The infrared (IR) is invisible radiant energy, electromagnetic radiation that we cannot see with our eyes, but we can sometimes feel on our skin as heat. The infrared light falls just outside the visible spectrum, beyond the edge of what we can see as red. Most of the thermal radiation emitted by objects near room temperature is infrared.

The circuit uses a MCP6032 microchip operational amplifier. The MCP6032 operational amplifier (op amp) has a gain bandwidth of 10kHz with a low typical operating current of 900nA and an offset voltage that is less than 150uV. The MCP6032 uses Microchip’s advanced CMOS technology, which provides low bias current, high-speed operation, high open-loop gain and rail-to-rail input and output swing. The MCP6032 operates with a single supply voltage that can be as low as 1.8V, while drawing less than 1uA of quiescent current. The MCP6032 is available in standard 8-lead SOIC and MSOP packages. It also includes, a PID20 integrated circuit and a few electronic components. The size of the output signal of PID20 is determined by the task at pins 3 and 4. The output signal at pin 3 is compared with a reference voltage equal to half the supply voltage. The reference voltage is taken from the voltage divider R2-R3-R4-R5. When approaching an object warmer than the surrounding environment, or to remove an object colder than the environment, the output voltage increases. The variation of the sensor output will be compared, the IC2a and IC2b, located voltage of 0.5V under and over voltage reference respectively. Depending on the output, one of the comparators calculates and activates T1.

This basic circuit is used in night-vision devices with infrared illumination, which allows people or animals to be observed without the observer being detected. The infrared light is also used in industrial, scientific, and medical applications as well as in consumer devices.

Passive Infrared Detector Circuit – [Link]

Build an op amp with three discrete transistors


by Lyle Russell Williams:

You can use three discrete transistors to build an operational amplifier with an open-loop gain greater than 1 million (Figure 1). You bias the output at approximately one-half the supply voltage using the combined voltage drops across zener diode D1, the emitter-base voltage of input transistor Q1, and the 1V drop across 1-MΩ feedback resistor R2.

Build an op amp with three discrete transistors – [Link]

Measure small currents without adding resistive insertion loss


by Maciej Kokot @ edn.com:

In most cases, you measure current by converting it into a proportional voltage and then measuring the voltage. Figure 1 shows two typical methods of making the conversion. In one method, you insert a probing resistor, RP, in series with the current path and use differential amplifier IC1 to measure the resulting voltage drop (Figure 1a). A second method is a widely known operational amplifier current-to-voltage converter in which inverted IC1’s output sinks the incoming current through the feedback resistor (Figure 1b).

Measure small currents without adding resistive insertion loss – [Link]

Simple Acoustic Guitar Sound Receiver

This design of acoustic sound receiver features low power operational amplifier. It has rail-to-rail input/output and 0.85mA supply current per amplifier. It uses piezo speaker as its microphone that can be attached to easily due to its size and dimension.

The circuit is comprised of MCP6L91RT-E/OT 10 MHz, 850 µA operational amplifier that is used to amplify the sound signal. The low-pass filter is used to allow low frequency signal to pass while attenuating high frequency signal or above cut-off frequency of the system to prevent distortions and unnecessary signal. The piezo speaker is used as a microphone or a sound receiver in this circuit. Its size and dimensions is well suited for this application.

The circuit is suitable for different types of acoustic guitar. Since it can be attached easily, the old and other traditional instruments can be developed and modified so that it can continue its service even for the digital era. It can be interfaced to different applications which is not limited to musical instrument.

Simple Acoustic Guitar Sound Receiver – [Link]

LTC6268-10 – 4GHz Ultra-Low Bias Current FET Input Op Amp


The LTC6268-10 is a single 4GHz FET input op amp for high dynamic range and high speed transimpedance amplifier (TIA) applications. This new decompensated amplifiers extend the speed and dynamic range capabilities of this ultralow bias current op amp family for applications with a gain of 10 or higher. Input bias current is 0.9pA max over the 40°C to 85°C temperature range and just 4pA max over the entire 40°C to 125°C temperature range. Wideband voltage and current noise are 4nV/√Hz and 7fA/√Hz, respectively. With 0.45pF input capacitance and 1000V/μs slew rate, the LTC6268-10 is well suited for photodiode and photomultiplier (PMT) circuits, high impedance sensor applications and for driving analog to digital converters (ADCs). The part is also available as a dual op amp (LTC6269-10) and in unity gain stable options (single LTC6268 and dual LTC6269).

LTC6268-10 – 4GHz Ultra-Low Bias Current FET Input Op Amp – [Link]


Dual op amp affords 30-µV precision


by Susan Nordyk @ edn.com

Supplied in an 8-lead MSOP, the LT6023 dual micropower op amp from Linear Technology provides an input offset voltage of 30 µV maximum and settles to 0.01% in 60 µs, making it useful for multiplexed data-acquisition systems and precision signal processing. Proprietary slew-enhancement circuitry results in a fast, clean output step response with low power consumption.

Specially designed input circuitry maintains high impedance, which minimizes current spikes associated with fast steps for input steps up to 5 V. Slew rate is 1 V/µs, while maximum supply current is 20 µA/amplifier. The LT6023 also includes a shutdown mode that reduces supply current to less than 3 µA when the part is not active. An enable time of 480 µs and a fast slew rate combine to provide power-efficient operation in duty-cycled applications.

Dual op amp affords 30-µV precision – [Link]

OpAmps Tutorial – What is an Operational Amplifier?

The most often requested video! In this tutorial Dave explains what Operational Amplifiers (OpAmps) are and how they work. The concepts of negative feedback, open loop gain, virtual grounds and opamp action. The comparator, the buffer, the inverting and non-inverting amplifiers, the differential amplifier, and the integrator circuit configurations are also explained.
Then a practical breadboard circuit to demonstrate a virtual ground and the effect of voltage rail limitations.

OpAmps Tutorial – What is an Operational Amplifier? – [Link]

App note: Does your op amp oscillate?


All about Op Amp stability app note from Linear Technology.

Well, it shouldn’t. We analog designers take great pains to make our amplifiers stable when we design them, but there are many situations that cause them to oscillate in the real world. Various types of loads can make them sing. Improperly designed feedback networks can cause instability. Insufficient supply bypassing can offend. Finally, inputs and outputs can oscillate by themselves as one-port systems. This article will address common causes of oscillation and their remedies.

App note: Does your op amp oscillate? – [Link]

New zero-drift Op Amps


by elektor.com:

Two new low-cost, op amps with close to zero drift operation and low operating quiescent current have been introduced by On Semiconductor. Typical applications include front-end amplifier circuits and power management designs. The NCS325 and NCS333 provide rail-to-rail input and output performance and are optimized for low voltage operation of 1.8 V to 5.5 V. the op amps feature a quiescent operating current of 21 µA and 17 µA respectively at 3.3 V. The devices operate with a gain bandwidth of 350 kHz with ultra-low peak to peak noise down to 1.1 µV from 0.1 Hz to 10 Hz.

New zero-drift Op Amps – [Link]

Visualizing comparator and Op Amp hysteresis


Kerry Wong writes:

Hysteresis can be added to a comparator circuit to improve its stability, especially when the input signal is noisy. In this post, we will examine the hysteresis characteristics of some common comparator and Op Amps using an oscilloscope.
Perhaps the most intuitive way to visualize the hysteresis in a circuit is to plot the input signal (x axis) against the output signal (y axis). So, if we sweep the input voltage we should be able to see the characteristics of the transitioning of the output voltage due to hysteresis.

Visualizing comparator and Op Amp hysteresis – [Link]