Simple Op-amp IC Tester Circuit

Operational amplifiers, often known as op-amps, are essential parts of electronics that are used extensively in filtering, amplification, and analog signal processing.

Maintaining the functionality and dependability of a circuit requires testing an op-amp integrated circuit IC before utilizing it.

To swiftly and simply confirm an op-amps fundamental operation, an op-amp IC tester circuit is developed.

An operational amplifier Op-amp is essentially a Voltage Comparator with two inputs: an inverting input and a non-inverting input.

When the voltage at the non-inverting input (+) surpasses the voltage at the inverting input (-), the comparators output is considered high.

Additionally, the output is LOW if the voltage of the inverting input (-) is higher than the non-inverting end (+).

Because of their high gain, op-amps are typically used as voltage amplifiers.

Op-amps have one comparator or several, like in the case of LM741 op-amp

This article provides a simple circuit design for an op-amp tester that makes use of the LM741 op-amp and a few additional passive parts.

Circuit Working:

Parts List:

The LM741 op-amps operational capability is tested using the simple op-amp IC tester circuit.

An LM741 op-amp, resistors, diodes, capacitor, LED, and a 9V power source make up the circuit.

Here is a detailed information of how the circuit works:

To make things simpler, a single 9V supply is used in this circuit.

Place the LM741 op-amp correctly on the board.

If the op-amp is working properly, the LED will blink or flash, and if it is not the LED will either always be ON or off.

The circuit operates simply; if the op-amp is operational, it will produce a square wave at the output, which will cause the LED to blink.

When the op-amp circuit is turned on, the output of the LM741 pin 6 op-amp is high and the voltage at the non-inverting input (+) is initially greater than the value at the inverting input (-).

As a result, capacitor C1 begins to charge through resistor R2, and the output drops when the voltage at the inverting terminal pin 2 is exceeded by the charging of C1.

Additionally, capacitor C1 begins to discharge when the output drops below the non-inverting terminal of the comparator, which causes the output to rise once more.

The result of this operation, which is repeated endlessly, is a square wave, which causes the LED to blink.

As a result, if the Op-amp is functioning properly, the LED will blink constantly at regular intervals; if not the LED will either remain ON or turn off.

Formulas:

The following formulas pertain to the LM741 op-amp used in the Simple Op-Amp IC Tester Circuit and aid in deriving and interpreting the circuits behavior:

Formula for Voltage Divider:

To determine the reference voltage applied to the op-amps non-inverting input, utilize the voltage divider formula.

V_ref​ = V_in​ × R2​​ / R1​ + R2​

where,

• Vref​ is the Reference voltage at the non-inverting input.
• Vin is the Input voltage from the power supply of 9V
• R1​ and R2 are the resistances in the voltage divider.

LED Current Estimation:

It is crucial to figure out the current passing through the LED to make sure it functions properly.

Ohms Law can be applied in this way:

I_LED ​= V_out​−V_LED​​ / R_LED​

where,

• ILED​ is the current through the LED.
• Vout is the output voltage of the op-amp
• VLED is the the forward voltage drop of the LED
• RLED is the resistor connected with the LED

Op-Amp Gain Calculation:

The gain G of the op-amp in the basic buffer arrangement should ideally be 1.

This is computed using: G = V_out​​ / V_in​

where,

• Vout​ is the output voltage of the op-amp.
• Vin is the input voltage to the non-inverting input.

In the case of a voltage follower arrangement, Vout should equal Vin, hence gain G should be as follows:

G = 1

Impedance of Capacitor:

High-frequency noise is filtered in part by the capacitor.

Its impedance Z_C, is determined by:

Z_C ​= 1​ / jωC

where,

• ZC​ is the impedance of the capacitor.
• j is the imaginary unit (√-1​)
• ω is the angular frequency (ω = 2πf) where f is the frequency of the noise.
• C is the capacitance of the capacitor.

The capacitor should have a low impedance at the relevant frequencies (usually high frequencies) for efficient filtering.

Diode Voltage Drop:

The circuits diodes provide reverse polarity protection.

Every diode has a forward voltage drop, or VD for silicon diodes, for example, this is typically around 0.7V.

One can compute the real voltage drop as follows:

V_D​ = I_D​ × R_D​ + V_D,0​

where,

• VD​ is the voltage drop across the diode.
• ID is the current through the diode.
• RD is the resistance in the diodes path
• VD,0 is the diodes intrinsic forward voltage which is around 0.7V for silicon diodes.

These formulas help in the design and comprehension of the behavior of the circuit, guaranteeing that the op-amp tester performs as needed.

How to Build:

To build a Simple Op-amp IC Tester Circuit follow the below mentioned connections steps:

• Gather all the components mentioned in the above circuit diagram.
• Connect pin 2 of IC LM741 with two 1N4148 diodes configured with opposite polarity and a 10k resistor R3.
• Connect the opposite ends of the two diodes to pin 3 of IC LM741 and the junction of R4, R5 and R6 resistors.
• Connect the other end of R6 resistor to ground, R4 to the positive supply and R5 to pin 6 of LM741.
• Connect pin 4 of IC LM741 to ground.
• Connect pin 7 of IC LM741 to positive supply of +9V.
• Connect capacitor C1 between junction of R2, R3 and the positive supply.
• Connect the other end of R2 with pin 6 of IC LM741.
• Connect pin 6 of IC LM741 to ground through resistor R1 and LED1.

Conclusion:

An efficient and simple to assemble instrument for evaluating an op-amp integrated circuits operation is the Simple Op-Amp IC Tester Circuit using LM741.

By assembling this simple circuit, users may check the LED indication to see if an LM741 op-amp is functioning properly.

The op-amps basic functionality, including its capacity to manage input and output voltages within the anticipated range, is tested using this circuit.

References:

Circuit: Op-Amp Tester