This is the best Instrumentation OpAmp, Great CMRR, ensure supply has no ripple and keep analog and digital grounds separate. Ri can be replaced with a trimpot and resistor to alter gain. Connect a preset ends to pins 1 and 8 and preset wiper to VCC for Offset Null when high gains are configured.
Instrumentation Amp - Op-Amp Designs
The Input zeners and diodes form a protective clamp for all voltages above VCC-VDD. If supply is changed to +12 -12 change zeners to 12V zeners. Use similar Zeners at output to protect Output from being zapped by over-voltages or high energy - voltage or frequency transients. Add plastic capacitors across Rf for damping AC operation or ripple. Also avoid floating inputs by providing a bias, till you connect it to a sensor; or you will see electrometer like effects.
Category: "Analog-Opamps"
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Posted by dapj20 on Jul 03, 2019 in Analog-Opamps
This is an Op-Amp Tutorial. Here you see an Operational Amplifier in the Inverting Amp configuration. I have used OP07 as it is almost like an ideal Opamp. The ultra low offset is the best part. Then not really, CA3140 has a Tera Ohm Input resistance but offset not the best. ICL7650 approaches an Ideal Op-Amp and chopper stabilized.

These parameters are good for DC Amps. Sensors, Strain Gauge Bridges Signal Conditioning need them. Then when you want a better AC performance, you can use a LF353 with a nice slew rate. Here the DC merits are not of much use.
Inverting Amplifier - Op-Amp Circuits
Input Impedance of this module is Ri as pin 2 is at virtual ground, the opamp with feedback tries to maintain pin 2 and 3 at same potential pin 3 is at 0V hence pin 2 is at virtual ground. Clamping diodes protect OpAmp, Rf + Ri is between 5kE and 1ME as an opamp may be able to drive around say 5mA max
Current into node pin 2 = Vin/Ri if Vin is +ve it raises potential at pin 2, in order to bring it to 0V the OpAmp sucks away the current by turning its output negative the current leaving pin 2 node is also Vin/Ri. Then Vout is given by Vin/Ri * Rf as per V=IR ohms law. Most OpAmps output swings around 1v less than VCC/VDD for full swing use CA3130 this is a FET input OpAmp, and has low bias currents in pico amps.
Slide the Potentiometers just like you would operate a Sliding Control. Drag the Knob on Pot to increase or decrease the resistance. The Resistance is shown is blue letters and dynamically alters value as you slide the pot. Both Rf and Ri have Pots which are variable resistors.
The mV Source is varied by just moving mouse pointer over the two buttons, no clicking. This reduces finger strain and also you have a long lasting mouse. The mV buttons are special, the variation picks up speed if you let the mouse pointer remain on the button. This is Ramp-up and Ramp-down. This enables you to set it faster with just two buttons. This mV Source sets Vin.
The mV DPM at Output shows Vout. Vin and Vout are in mV. The formula you know
Values are to give an idea, keep in mind Battery Consumption, Source Impedance and what the Op-Amp need to drive. Most Op-Amps today are short circuit protected but even little loading will upset your equations. Very high resistance, even above 1M, careful PCB design is required. Leakage currents on PCB will play spoilsport. A little sunshine and moisture, there can be copper sulfate formation on terminals and tracks on exposed PCB. There is no formula for that. Theory and Practice in Tandem, this works.
Never drive any Opamp pin to a voltage higher than the supply +/- dual supply. Use clamping diodes, read specs well.
The Force does not happen to everybody. You have to master your Theory and Formulas. You then have to Experiment, Try out and Understand in detail. Then you shall modify, create & Juggle circuits !

These parameters are good for DC Amps. Sensors, Strain Gauge Bridges Signal Conditioning need them. Then when you want a better AC performance, you can use a LF353 with a nice slew rate. Here the DC merits are not of much use.
Inverting Amplifier - Op-Amp Circuits
Input Impedance of this module is Ri as pin 2 is at virtual ground, the opamp with feedback tries to maintain pin 2 and 3 at same potential pin 3 is at 0V hence pin 2 is at virtual ground. Clamping diodes protect OpAmp, Rf + Ri is between 5kE and 1ME as an opamp may be able to drive around say 5mA max
Current into node pin 2 = Vin/Ri if Vin is +ve it raises potential at pin 2, in order to bring it to 0V the OpAmp sucks away the current by turning its output negative the current leaving pin 2 node is also Vin/Ri. Then Vout is given by Vin/Ri * Rf as per V=IR ohms law. Most OpAmps output swings around 1v less than VCC/VDD for full swing use CA3130 this is a FET input OpAmp, and has low bias currents in pico amps.
Slide the Potentiometers just like you would operate a Sliding Control. Drag the Knob on Pot to increase or decrease the resistance. The Resistance is shown is blue letters and dynamically alters value as you slide the pot. Both Rf and Ri have Pots which are variable resistors.
The mV Source is varied by just moving mouse pointer over the two buttons, no clicking. This reduces finger strain and also you have a long lasting mouse. The mV buttons are special, the variation picks up speed if you let the mouse pointer remain on the button. This is Ramp-up and Ramp-down. This enables you to set it faster with just two buttons. This mV Source sets Vin.
The mV DPM at Output shows Vout. Vin and Vout are in mV. The formula you know
Vout = Vin * (-1) * (Rf / Ri)
A real pot has a Minimum 0 ohms value, but in these pots i have shown 10K as min. Even in a real design, depending on input source impedance and output voltage the resistors are better kept high. Never go less than 4.7K, the OpAmp loads or the source, even another opamp stage or sensor loads. These can be resolved by using buffers or power amps respectively, if such a need arises. For all analog computing/signal conditioning use 10K min. Battery operated designs have 100K as min and FET amps only.Values are to give an idea, keep in mind Battery Consumption, Source Impedance and what the Op-Amp need to drive. Most Op-Amps today are short circuit protected but even little loading will upset your equations. Very high resistance, even above 1M, careful PCB design is required. Leakage currents on PCB will play spoilsport. A little sunshine and moisture, there can be copper sulfate formation on terminals and tracks on exposed PCB. There is no formula for that. Theory and Practice in Tandem, this works.
Never drive any Opamp pin to a voltage higher than the supply +/- dual supply. Use clamping diodes, read specs well.
The Force does not happen to everybody. You have to master your Theory and Formulas. You then have to Experiment, Try out and Understand in detail. Then you shall modify, create & Juggle circuits !
Posted by dapj20 on May 03, 2019 in Analog-Opamps
A very simple one op-amp diff amp. This amplifies the difference between two inputs Vp and Vn the low impedance of this configuration is a drawback, but can be used in analog computing. Optimum VCC VDD can be +12/-12. AC signals common to Vp and Vn are canceled by this configuration.
Differential Amplifier - Op-Amp Circuits

Use a capacitor like 10nF plastic from pin 2 to 3 or across R2 to make circuit stable. For AC applications use LF351 TLO71 as they have good slew rate and also are FET inputs. For AC applications use a capacitor (1uF) in series with Ri to block DC Components.
The Inputs have asymmetrical input impedance this affects CMRR, also use 1% tolerance MFR resistors for Rf and Ri.
Vout = ( Vp - Vn ) * ( Rf / Ri )
Slide the Potentiometers just like you would operate a Sliding Control. Drag the Knob on Pot to increase or decrease the resistance. The Resistance is shown is blue letters and dynamically alters value as you slide the pot.
Differential Amplifier - Op-Amp Circuits

Use a capacitor like 10nF plastic from pin 2 to 3 or across R2 to make circuit stable. For AC applications use LF351 TLO71 as they have good slew rate and also are FET inputs. For AC applications use a capacitor (1uF) in series with Ri to block DC Components.
The Inputs have asymmetrical input impedance this affects CMRR, also use 1% tolerance MFR resistors for Rf and Ri.
Vout = ( Vp - Vn ) * ( Rf / Ri )
Slide the Potentiometers just like you would operate a Sliding Control. Drag the Knob on Pot to increase or decrease the resistance. The Resistance is shown is blue letters and dynamically alters value as you slide the pot.
Posted by dapj20 on May 03, 2019 in Analog-Opamps
If output impedance of a point is a high value then connecting another circuit at that point will load it, resulting in malfunction or error. Buffers are used as interface between circuits.
Low impedance of an output means it can source/sink lot of current, when you need 2 opamps use LF353 or TL072 which are dual opamps.

Buffer Unity Gain Amp - Op-Amp Designs
A non-inv FET input is the best buffer, for inverting buffer use high R values. Using very high R values like 2.2M or higher requires a glass epoxy PCB and guard rings around pin 2, 3 to prevent leakage currents on the PCB reaching the PINs.
Also moisture and dust has to be prevented by using RTV coating or Varnish. Use 78L05 and 79L05 for the dual supply required by this circuit.
Low impedance of an output means it can source/sink lot of current, when you need 2 opamps use LF353 or TL072 which are dual opamps.

Buffer Unity Gain Amp - Op-Amp Designs
A non-inv FET input is the best buffer, for inverting buffer use high R values. Using very high R values like 2.2M or higher requires a glass epoxy PCB and guard rings around pin 2, 3 to prevent leakage currents on the PCB reaching the PINs.
Also moisture and dust has to be prevented by using RTV coating or Varnish. Use 78L05 and 79L05 for the dual supply required by this circuit.
Inverting Amp - Vout = -1 * Vin
Non-Inverting Amp - Vout = Vin
Vary the Millivolt Source by just hovering your Mouse pointer over the Two Buttons (Increment and Decrement). If you leave the mouse pointer on a button, the variation will pick up speed. Set a Value of your choice, positive or negative, you can set from -199.9mV to +199.9mV. Note the Output values on both the DVMs on the right (digital Volt Meter) in a Table. Repeat this for at-least 7 readings of both polarities. Jot the Formula below in your book and relate it to your table. Posted by dapj20 on Apr 06, 2019 in Analog-Opamps
The Input Impedance of this module is very high and is symmetric. This circuit can be used for strain gauges and for four wire measurements. If inputs are in mV use OP07. The merit is that it uses only 2 OpAmps yet has high differential Input Impedance.
Dual Differential Amp - Op-Amp Designs

The Outputs of Opamps are low impedance but still have limits they cannot drive more than a few mA of Current into the Load. If low ohmic value loads are to be applied use external transistors as amplifiers. If inputs Vn-Vp are floating, outputs may be random or oscillating, it is good to have a bias network of 10M resistors to a potential even zero or common, this enables some Vout when input floats.
Vout = (Vp - Vn) * (Rf + Ri) / Ri
The Variable Resistor or Sliding Potentiometer for Rf and Ri are present for Gain Setting. Slide them to vary Rf and Ri, Assume both Rf values vary in tandem, when you slide the Rf Pot. Like a Ganged Pot or Dual Pot. Even Ri is a Dual Pot that varies both Ri Simultaneously. Now set the mV of Vp and Vn using the mV Sources provided. Just Hover Mouse pointer over buttons, variation ramps up if mouse pointer is left on the buttons. No pressing Buttons here. Take the Vout readings, tabulate the Results.
Dual Differential Amp - Op-Amp Designs

The Outputs of Opamps are low impedance but still have limits they cannot drive more than a few mA of Current into the Load. If low ohmic value loads are to be applied use external transistors as amplifiers. If inputs Vn-Vp are floating, outputs may be random or oscillating, it is good to have a bias network of 10M resistors to a potential even zero or common, this enables some Vout when input floats.
Vout = (Vp - Vn) * (Rf + Ri) / Ri
The Variable Resistor or Sliding Potentiometer for Rf and Ri are present for Gain Setting. Slide them to vary Rf and Ri, Assume both Rf values vary in tandem, when you slide the Rf Pot. Like a Ganged Pot or Dual Pot. Even Ri is a Dual Pot that varies both Ri Simultaneously. Now set the mV of Vp and Vn using the mV Sources provided. Just Hover Mouse pointer over buttons, variation ramps up if mouse pointer is left on the buttons. No pressing Buttons here. Take the Vout readings, tabulate the Results.
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