Operational Amplifiers. Chris Nygren Matt Livianu Brad Schwagler. Introduction Background Amplifier Introduction Basic Circuits Review Characteristics of an Ideal Op Amp Types of Op Amps Practical Applications Conclusion Quiz. Agenda. To introduce the Operational Amplifier by
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 popularBackground
Uses: Amplify…straight up
Uses: Analog inverter
Uses: Low-voltage alarms, night light controller
Uses: Motor controllers
Uses: Add multiple sensors inputs until a threshold is reached.
If all resistors are equal:
Uses: PID Controller
(where Vin and Vout are functions of time)
Band-pass filter cascades both high-pass and low-pass!
Voltage suffers losses due to resistances in path
Low impedance is better for resisting noise
So how do we generate a constant current source?
Transconductance AmplifierMeasuring current
- In: Sensors (temp, pressure, etc),
- Out : Radios (Variable Freq Osc)
Can you use an Op-Amp as a buffer? If so, How?
Why should you care about the device bandwidth rating?
What is the most common Op Amp chip?
What is an ‘active’ component? Is an Op Amp an active or a passive component?
What is the advantage of an active vs. passive filter?Questions?
• Good low resistance, twisted, and shielded wire should be used when a sensor is located far away from the op-amp circuit.
• Minimize current draw in sensor circuits to reduce thermal drift
• Filter power into op-amp circuits using capacitors
• Design op-amp circuits so output cannot be negative in order to protect 68HC11 A/D port.
• Isolate op-amp circuit output with unity gain op-amp if connected to an actuator.
• Make sure bandwidth of op-amp is adequate
• Use trimmer potentiometers to balance resistors in differential op-amp circuits
• Samples of op-amps can be obtained from National Semiconductor (http://www.national.com)Practical Tips