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UNIT 12Task 1. Match the words and phrases with the translations.
TASK 2. Read the text about amplifiers and complete it with the words and phrases.
… is a device that 2) … a small input signal (voltage, current, or power) and 3) … a larger 4) … that contains the essential 5) … features of the 6) … . Amplifiers of various types are widely used in such electronic equipment as radio and television 7) …, 8) … audio equipment, and computers. Amplifying action can be provided by electromechanical devices (e.g., transformers and generators) and vacuum tubes, but most electronic systems now 9) … solid-state microcircuits as amplifiers. Such an integrated circuit consists of many thousands of transistors and related devices on a single tiny silicon chip.
A single amplifier is usually not enough 10) … the output to the desired 11) …. In such cases the output of the first amplifier is 12) … a second, whose output is fed to a third, and so on, until the output level is 13) …. The result is cascade, or 14) … amplification. Long-distance telephone, radio, television, electronic control and measuring instruments, radar, and countless other devices all depend on this basic process of amplification. The 15) … amplification of a multistage amplifier is the product of the 16) … of the individual stages.
There are various schemes for the 17) … of cascading electronic amplifiers, depending upon the nature of the signal 18) … in the amplification process. 19) … microcircuits are better than vacuum-tube circuits for the direct coupling of 20) … amplifier 21) … . Transformers can be used for coupling, but they are too big and expensive.
An electronic amplifier can be designed to produce a 22) … output signal identical in every respect to the input signal. This is linear operation. If the output is altered in shape after passing through the amplifier, amplitude 23) … exists. If the amplifier does not amplify equally at all frequencies, the result is called frequency distortion, or discrimination. task 3. Answer the questions below and retell the text. What is the main purpose of the amplifier? 2. Where are amplifiers used? 3. What electromechanical devices are used to provide the amplification of the input signals? 4. What can be done in case if the single amplifier is not enough to get a desired level of signal? 5. What are the examples of devices which depend on the multistage amplification? 6. What is the overall amplification of the multistage amplifier due to? 7. Why are microcircuits better for coupling than transformers? 8. What causes amplitude distortion? TASK 4. Match the names with the descriptions. Current amplifier Transresistance amplifier Voltage amplifier Transconductance amplifier The four basic types of amplifiers are as follows: This is the most common type of amplifier. An input voltage is amplified to a larger output voltage. The amplifier’s input impedance is high and the output impedance is low. This amplifier changes an input current to a larger output current. The amplifier’s input impedance is low and the output impedance is high. This amplifier responds to a changing input voltage by delivering a related changing output current. This amplifier responds to a changing input current by delivering a related changing output voltage. Other names for the device are transimpedance amplifier and current-to-voltage converter. TASK 5. Watch the video about amplifiers and complete the following tasks. Before watching the video, match the words and their meanings.
After watching the video, answer the following questions. 1. What is this part of the tutorial about? 2. What is the easiest type of an amplifier for beginners? 3. What is the function of an amplifier? 4. What is the “gain” of the amplifier? 5. How many pins were shown in a bare op amp circuit? 6. What do plus and minus on the diagram mean? 7. What minimum voltage supplies values should you have? 8. What might happen if you don’t give your op amp enough voltage? 9. Why do you need to use capacitors in your circuit? 10. How can you get a really good positive and negative voltage supply for your op amp? Listen to the second part of the video and fill in the gaps. Now, this thing alone isn’t going to be able to 1) … anything. You’ve got to have a couple of other components to 2) … your op amp to have a right 3) …. I’m going to show you one of the simplest amplifier 4) … you can build – a classic non-inverting amplifier. With a non-inverting amplifier you set the gain with 5) …. The gain is given by one plus R2 60 … R1. So if R1 is 2 kOhms and R2 is ten kOhms, you’ll get a gain of 1 + 5 which would be 6. You usually want these resistors to be somewhere in kiloOhm 6) …. So an easy thing beginners can do is just let R1 be 1 kOhm and use this 7) … to calculate the 8) … of R2 to get the gain that you want. |