* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download 3.7 Operational amplifiers
Ground (electricity) wikipedia , lookup
Electronic musical instrument wikipedia , lookup
Current source wikipedia , lookup
Fault tolerance wikipedia , lookup
Signal-flow graph wikipedia , lookup
Electrical substation wikipedia , lookup
Flexible electronics wikipedia , lookup
Voltage optimisation wikipedia , lookup
Negative feedback wikipedia , lookup
Audio power wikipedia , lookup
Buck converter wikipedia , lookup
Earthing system wikipedia , lookup
Oscilloscope history wikipedia , lookup
Schmitt trigger wikipedia , lookup
Public address system wikipedia , lookup
Surface-mount technology wikipedia , lookup
Resistive opto-isolator wikipedia , lookup
Switched-mode power supply wikipedia , lookup
Rectiverter wikipedia , lookup
Mains electricity wikipedia , lookup
Two-port network wikipedia , lookup
Wien bridge oscillator wikipedia , lookup
3.7 Operational amplifiers The use of transistors requires many additional components. The invention of the integrated circuit in 1958 by Jack Kilby opened up a whole new era for electronics. Even the simplest Integrated circuits contain many transistors and the components needed to make a usable device. One of the most used integrated circuits for signal amplification is the 741. The 741 integrated circuit is contained in an 8 pin package and needs only two resistors to produce an amplified signal. 1 5 -input 2 +ve 2 6 output 7 - 6 741 +input 3 7 +ve -ve 4 3 + 4 -ve 8 Figure 3.32 Operational amplifier in an 8 pin Dual in Line package and circuit symbol The 741 has five pins that are used to build an amplifier. Normally the 741 operates using a Plus - Ground - Minus supply rather than a Plus-Minus supply like a battery. Figure 3.33 shows how a + 9volt - gnd - 9volt supply can be built from two batteries. -9V - 0V + +9V - + + +Ve 0V Gnd -Ve - + - Figure 3.33 Plus - Zero - Minus 9 Volt supply Acton Instruments – ANU 1 6/05/2017 If the power supply is constructed using two 9volt batteries as shown the circuit in figure 3.34 will work. Rf +9V Rin 2 7 - 6 741 microphone input 3 + 4 -9V output Gnd Figure 3.34 Building and using the integrated amplifier circuit. The gain is set by the values of Rf and Rin. Gain Rf Rin If Rin 10K calculate the value of Rf to give a gain of 10 When the circuit is operational monitor the waveforms on the oscilloscope and try different values of Rf to change the gain. With only a single 9 Volt battery a different approach has to be taken to make the device operate as an amplifier. The power supply is based around a voltage divider and with equal value resistors the centre voltage will be 4.5 volts. Build the circuit in figure 3.35 +9V 10K 1uF + 741 10K microphone 100K 1K + 10uF 0V Figure 3.35. 741 amplifier using a single battery Acton Instruments – ANU 2 6/05/2017 Identify the resistors that make up the voltage divider network. Measure the voltages. Calculate the gain of the amplifier from the resistor values. Try to think of an explanation (difficult) for the presence of the 10uF capacitor. Short it out and see what happens to the amplifier Acton Instruments – ANU 3 6/05/2017