CO2037 – Electrical Electronic Circuits Operational Amplifier (Op-Amp) Image Source: Internet CO2037 – Operational Amplifier (Op-Amp) Contents § Operation § Feedback Circuit § Characteristics § Practical Applications 2 CO2037 – Operational Amplifier (Op-Amp) 3 Basic Op-Amp § Op-Amp = Operational Amplifier § An Op-Amp consists of … ▫ Inverting input ▫ Noninverting input ▫ Output https://www.youtube.com/watch?v=kiiA6WTCQn0 CO2037 – Operational Amplifier (Op-Amp) 4 Op-Amp Gain § Op-Amps have a very high gain. They can be connected open-loop or close-loop. ▫ Open-loop refers a configuration where there is no feedback from output back to the input. In the open-loop configuration, the gain can exceed 105. ▫ Closed-loop configuration reduces the gain. In order to control the gain of an op-amp it must have feedback. This feedback is a negative feedback. A negative feedback reduces the gain and improves many characteristics of the op-amp. CO2037 – Operational Amplifier (Op-Amp) 5 Op-Amp Models § Practical Model ▫ Zin is very large ▫ Zout is small " ▫ The gain 𝐴! = !"# in open-loop configuration is very high. "$% § Ideal Model (used for analysis) ▫ Zin = ∞ ® Iin+ = Iin- = 0; Vin+ = Vin▫ Zout = 0 ▫ The open-loop gain: 𝐴! = "!"# "$% =∞ CO2037 – Operational Amplifier (Op-Amp) Op-Amp Operation § The amplitude of Vout is higer than amplitude of Vin. 6 CO2037 – Operational Amplifier (Op-Amp) Op-Amp Operation § The differential signal of 2 inputs is amplified. § When 2 inputs use common signal, the output is zero. 7 CO2037 – Operational Amplifier (Op-Amp) 8 Feedback Circuits § For the circuits without feedback (i.e. no connection between output and input), the open-loop gain is very large (>105). § The output voltage will easily reach the saturation and the amplitude will be trimmed. CO2037 – Operational Amplifier (Op-Amp) 9 Feedback Circuits § In order to control the gain of an op-amp it must have feedback. This feedback is a negative feedback. A negative feedback reduces the gain and improves many characteristics of the op-amp. CO2037 – Operational Amplifier (Op-Amp) 10 Inverting Op-Amp Gain https://www.youtube.com/watch?v=AuZ00cQ0UrE CO2037 – Operational Amplifier (Op-Amp) Non-Inverting Op-Amp § https://www.youtube.com/watch?v=uyOfonR_rEw 11 CO2037 – Operational Amplifier (Op-Amp) Op-Amp Datasheet § IC LM358 12 CO2037 – Operational Amplifier (Op-Amp) Op-Amp Datasheet (IC LM358) § Maximum power supply: ±22V § Maximum input voltage: ±15V § Maximum differential input voltage: ±30V 13 CO2037 – Operational Amplifier (Op-Amp) Op-Amp Datasheet § IC 741 14 CO2037 – Operational Amplifier (Op-Amp) Op-Amp Datasheet (µA741) § Điện thế hoạt động 3 đến 30 à nếu nguồn đôi là ±15V § Điện thế ngõ vào từ (Vcc-) – 0.3 đến (Vcc+) – 1.5 • AVD – Large-signal differential voltage amplification – 200V/mV = 200.000 • ri – input resistance: 2MW • ro – output resistance: 75W 15 CO2037 – Operational Amplifier (Op-Amp) Output Voltage Threshold 16 CO2037 – Operational Amplifier (Op-Amp) Practical Op-Amp Circuits § Unity Follower § Summing Amplifier § Integrator § Differentiator § Comparator 17 CO2037 – Operational Amplifier (Op-Amp) Unity Follower 18 CO2037 – Operational Amplifier (Op-Amp) Summing Amplifier https://www.youtube.com/watch?v=jsKSfaFQ4d4 19 CO2037 – Operational Amplifier (Op-Amp) Integrator 20 CO2037 – Operational Amplifier (Op-Amp) Differentiator 21 CO2037 – Operational Amplifier (Op-Amp) Comparator § Vout = +Vout(max) when V+ > V▫ Vin > VREF § Vout = -Vout(max) when V+ < V▫ Vin < VREF 22 CO2037 – Operational Amplifier (Op-Amp) Noisy Comparator § Unexpected pulses 23 CO2037 – Operational Amplifier (Op-Amp) Noiseless Comparator § Hysteresis ▫ 0 ®1 if Vin is greater than β threshold ▫ 1 ® 0 if Vin is smaller than α threshold 24 CO2037 – Operational Amplifier (Op-Amp) Application (1) § Protection Circuit using Op-Amp Comparator 25 CO2037 – Operational Amplifier (Op-Amp) Application (2) § Analog to Digital Conversion 26 CO2037 – Operational Amplifier (Op-Amp) IC 555 27 CO2037 – Operational Amplifier (Op-Amp) IC555 – Clock Pulse Generator 28 CO2037 – Operational Amplifier (Op-Amp) IC555 – Delay Circuit 29 CO2037 – Operational Amplifier (Op-Amp) Exercise 1 § Compute the output voltage in the following circuits using ideal op-amp 30 CO2037 – Operational Amplifier (Op-Amp) Exercise 1 – Solution 31 CO2037 – Operational Amplifier (Op-Amp) 32 Exercise 2 § Characteristics of an Op-Amp is given in the following table. The power supply is ±15V. Parameter Minimum Typical Output Voltage ±12V ±13.5V Input Voltage ±11V ±12.5V Output current of shorted-circuit ±12mA ±20mA § Determine VX Maximum CO2037 – Operational Amplifier (Op-Amp) Exercise 2 – Solution 33 CO2037 – Operational Amplifier (Op-Amp) 34 Exercise 3 § Characteristics of an Op-Amp is given in the following table. The power supply is ±15V. Parameter Minimum Typical Output Voltage ±12V ±13.5V Input Voltage ±11V ±12.5V Output current of shorted-circuit ±12mA ±20mA § Determine Vo when Vin=±6V Maximum CO2037 – Operational Amplifier (Op-Amp) Exercise 3 - Solution 35 CO2037 – Operational Amplifier (Op-Amp) 36 Exercise 4 § Characteristics of an Op-Amp is given in the following table. The power supply is ±15V. § Determine Vo Parameter Minimum Typical Output Voltage ±12V ±13.5V Input Voltage ±11V ±12.5V Output current of shorted-circuit ±12mA ±20mA Maximum CO2037 – Operational Amplifier (Op-Amp) Exercise 4 - Solution 37