Analogue Electronics Lecture 1: Operational Amplifiers (Op Amps) Lecture Notes PDF

Analogue Electronics Lecture 01 The Operational Amplifier (Op Amp) Dr. Ibrahim Salah Ibrahim Control and Computer Eng. Dept. Faculty of Engineering Almaaqal University References [Razavi, 2013] and [Alexander-Sadiku, 2015]  Operational Am...

Analogue Electronics Lecture 01 The Operational Amplifier (Op Amp) Dr. Ibrahim Salah Ibrahim Control and Computer Eng. Dept. Faculty of Engineering Almaaqal University References [Razavi, 2013] and [Alexander-Sadiku, 2015]  Operational Amplifier-Op Amp  Op amps are amplifiers that can be used to implement mathematical operations  Summation, difference, integration, differentiation, etc.  That’s why they are called: operational amplifiers  It is an electronic unit that behaves like a voltage-controlled voltage source.  Internally, they are formed of multiple stages of transistor amplifiers  Terminals  1: Inverting terminal  2: Non-inverting terminal  3: Output terminal  Op Amp Example  Several op amps may exist in the same package A typical op amp: (a) pin configuration, (b) circuit symbol  Ideal Op Amp characteristics  Infinite gain  Infinite input impedance  Zero output impedance  Infinite speed  The Inverting Configuration  Inverting amplifier reverses the polarity of the input signal while amplifying it  Our goal is to obtain the relationship between the input voltage vi and the output voltage vo. Applying KCL at node 1, Rf vo   vi R1 Example 1 Refer to the op amp below. If vi = 0.5V, calculate: (a) the output voltage, vo and (b) the current in the 10k resistor. Ans: (a) -1.25V; (b) 50μA Example 2  The Summing Amplifier  A summing amplifier is an op amp circuit that combines several inputs and produces an output that is the weighted sum of the inputs.  It takes advantage of the fact that the inverting con- figuration can handle many inputs at the same time.  Applying KCL at node a gives  The Summing Amplifier We note that va = 0 and substitute in above Eq. We get  indicating that the output voltage is a weighted sum of the inputs.  Needless to say, the summer can have more than three inputs.  Example 3 Calculate vo and io in the op amp circuit in Fig. The Inverting Configuration with General Impedances Thank you!  Home Work 1- what are the main characteristics of ideal Op Amp ? 2- Find the output of the op amp circuit shown in Fig. Calculate the current through the feedback resistor.  Home work Find vo and io in the op amp circuit shown in Fig.