كلية التقنية الصناعية مصراتة عنوان العرض Using op-Amps to build the control model إعداد الطالب :أحمد ا ّمحمد الشريمي رقم القيد112151536 : أستاذ المقرر :د.إسحاق األرباح Content Introduction What is an Op-Amp? Types of Op Amps Characteristics of the ideal op amp Practical applications to build the control model Summary o Introduction • Operational Amplifiers are represented both schematically and realistically below: – Active component! • Originally invented in early 1940s using vacuum tube technology – Initial purpose was to execute math operations in analog electronic calculating machines. • • Shrunk in size with invention of transistor Most now made on integrated circuit (IC) – Only most demanding applications use discrete components. • Huge variety of applications, low cost, and ease of mass production make them extremely popular o What is an Op-Amp? An Operational Amplifier (known as an “Op-Amp”) is a device that is used to amplify a signal using an external power source Op-Amps are generally composed of: Transistors, Resistors, Capacitors = + + Brief History • First patent for Vacuum Tube Op-Amp (1946) • First Commercial Op-Amp available (1953) • First discrete IC Op-Amps (1961) • First commercially successful Monolithic OpAmps (1965) History Continued… • Leading to the advent of the modern IC which is still used even today (1967 – present) Electrical Schematic of μA741 Op-Amps and their Math A traditional Op-Amp: V+ VVout Vs+ Vs- : : : : : non-inverting input inverting input output positive power supply negative power supply Vout = K (V+ - V-) • The difference between the two inputs voltages (V+ and V-) multiplied by the gain (K, “amplification factor”) of the Op-Amp gives you the output voltage • The output voltage can only be as high as the difference between the power supply (Vs+ / Vs)and ground (0 Volts) o Types of Op Amps • • • • • Open Loop vs Closed Loop Ideal Op Amp Non-inverting Amplifier Inverting Amplifier Common Mode Input Open Loop vs Closed Loop A closed loop op-amp has feedback from the output to the input, an open loop op-amp does not Open Loop Closed Loop Ideal Op Amp i i 1) v v VDD VSS v0 VDD + vo - VSS v0 Av v v The open-loop gain, Av, is very large, approaching infinity. 2) i i 0 The current into the inputs are zero. Non-inverting Amplifier v vi v R1 + vo Closed-loop voltage gain AF - vo vi R2 vi v v R1 vo R1 R2 vo R2 AF 1 vi R1 Inverting Amplifier R2 Current into op amp is zero v v 0 v 0 vi ii i R1 R1 0 v0 v0 ii R2 R2 vi ii ii R1 v v + vi v0 R1 R2 AF vo R 2 vi R1 vo Common Mode Input Two signals of same phase, frequency, and amplitude are applied to the inputs which results in no output (signals cancel). But, in practical, a small output signal will result. This is called common-mode rejection. This type of mode is used for removal of unwanted noise signals. o Characteristics of the ideal op amp • Open-loop gain G is infinite • Rin is infinite • Zero input current • Rout is zero Ideal Op-Amp Practical Op-Amp Ideal Op-Amp o Practical applications to build the control model Applications – Filters Simulation of a Closed-Loop System Applications-PID Controller – System Circuit Diagram Applications- PI Control Applications - Filters Types: •Low pass filter •High pass filter •Band pass filter •Cascading (2 or more filters connected together) C R2 Low pass filter transfer function R1 Low pass filter Cutoff frequency + - + Vcc + - Vcc + V0 __ Simulation of a Closed-Loop System Figure (a) is a block diagram of a speed control system, the motor shaft speed w being controlled by the input voltage, Ví. Voltage Vi is derived from the tachogenerator and is compared with the input voltage to give the error signal, which is used to control the pulse generator and thyristor. The analogue computer block diagram is shown in Fig (b). The input voltage change is set on a potentiometer, shown as Ví. The amplifier, in the actual system, is replaced by a summing amplifier in the simulator. The thyristor and its pulse generator Simulation of a control System of an analogue computer PID Controller – System Block Diagram P VSET VERROR I Output Process D VSENSOR Sensor •Goal is to have VSET = VOUT •Remember that VERROR = VSET – VSENSOR •Output Process uses VERROR from the PID controller to adjust Vout such that it is ~VSET VOUT Applications PID Controller – System Circuit Diagram Signal conditioning allows you to introduce a time delay which could account for things like inertia System to control Calculates VERROR = -(VSET + VSENSOR) -VSENSOR Applications PID Controller – PID Controller Circuit Diagram VERROR PID VERROR Adjust Change Kp RP1, RP2 Ki RI, CI Kd RD, CD Applications of Op-Amps • Example of PI Control: Temperature Control • Thermal System we wish to automatically control the temperature of: • Block Diagram of Control System: Applications of Op-Amps • Example of PI Control: Temperature Control • Voltage Error Circuit: • Proportion al-Integral Control Circuit: summary ideal op amp: Output voltage limited to the range between V+ and V Ideal op amp is assumed to have Ri = ∞ W and Ro = 0 W. In the ideal op-amp, A is infinite ،In real op-amp, A is 20k to 200k Single- Input Mode Input signal is connected to ONE input and the other input is grounded. Inverting Mode :input signal at –ve terminal output opposite in phase to the applied input signal Non- Inverting Mode: input signal at +ve terminal output same polarity as the applied input signal common-mode will tend to reject noise. The Operational amplifiers deals with filters and controllers such as PID & PI and other controllers