Практическое занятие 17. Двухтактный усилитель

Lesson 1 7. Push - pull Amplifier

 

Read and learn the words:

  to feed (fed) - питать

to include - содержать, заключать (в себе)

to remain - оставаться

to push - толкать

to pull - тянуть

push-pull - пушпул, пушпульный

push-pull amplifier - двухтактный усилитель

push-pull circuit - двухтактная схема

push-pull transformer - пушпульный трансформатор

feedback - обратная связь

feedback amplifier - регенеративный усилитель

feedback coil - катушка обратной связи

feeding transformer - силовой трансформатор

Read and translate the text.  

Push-pull Amplifier

An amplifier is used to produce the output voltage greater than the input voltage. A push-pull amplifier includes two tubes. Their control grids are connected to the opposite ends of the input transformer secondary winding. The centre of this winding is connected to the tube cathodes. When maximum grid voltage is produced in one tube, minimum grid voltage is produced in the other tube. Thus, the sum of the plate currents remains constant.

The plate currents are fed into the opposite ends of the output transformer or a choke coil. It has its centre connected through the plate current supply to the cathodes. Thus direct current plate components are eliminated but alternating current components add in the circuit.

3. Complete these sentences, using the correct variant:

 

1. An amplifier is used

a) to separate a.c. from d.c.

b) to change the value of the input voltage.

 

2. The input voltage is increased

a) by means of a rectifier.

b) by means of an amplifier.

 

3. A push-pull amplifier includes

a) only one tube.

b) two tubes.

 

4. When maximum grid voltage is produced in one tube

a) maximum grid voltage is produced in the other tube.

b) minimum grid voltage is produced in the other tube.

 

5. The sum of the plate currents

a) changes.

b) remains constant.

 

6. D.c. components

a) are eliminated.

b) add in the circuit.

 

7. A.c. components

a) add in the circuit.

b) are eliminated.

 

4. Complete the sentences using while.

1. An amplifier is used to increase the value of the input voltage..........

2. When maximum grid voltage is produced in one tube..........

3. Direct current plate components are eliminated.........

 

5. Answer the following questions:

 

1. What is an amplifier used for?

2. By what means is a greater output voltage produced?

3. What are the main parts of a push-pull amplifier?

4. In what way are the tubes and the transformer connected?

5. Why does die sum of the plate currents remain constant?

6. Where are the plate currents fed?

7. What type of current is amplified by a push-pull amplifier?

8. What is the difference between a rectifier and an amplifier?

6. Say a few words about an amplifier and a rectifier. What do they have in common? What is the main difference between them?

 

Практическое занятие 17. Ступени усилителя, соединенные последовательно

Lesson 17. Amplifier Stages in Series

Read and learn the words:

 

bias - дополнительное (смещающее) напряжение

stage - каскад, ступень

to follow - следовать (за)

stage of amplification - ступень (каскад) усиления

grid bias - напряжение смещения

grid bias battery - сеточная батарея

grid plate capacitance - емкость анодной сетки

Read and translate the text.  

Amplifier Stages in Series

Amplifiers in use nowadays contain several stages. Sometimes their number is very great. Let us consider an amplifier including three stages. Its circuit uses three triodes connected in series. The circuit has a resistance as the plate load. A common plate voltage supply and a common grid bias are employed. The grid of each tube is insulated from the direct current component of the plate voltage by means of a capacitor. When the amplifier operates the voltage operation of the load

of one tube is applied to the grid of the next tube. The voltage variation is  transferred to the grid of the following tube through a capacitor. A change of  voltage on the first grid circuit results in an amplified plate current in the third stage.

 

3. Complete these sentences, using the correct variant:

1. Amplifiers in use nowadays

a) include only one stage,

b) include several stages.

 

2. A three-stage amplifier uses

a) three triodes connected in parallel.

b) three triodes connected in series.

 

3. The grid of each tube is insulated

a) by means of a coil.

b) by means of a capacitor.

 

4. The voltage variation is transferred

a) through a tube.

b) through a capacitor.

 

5. The circuit uses

 a) a different grid bias.

b) a common grid bias.

 

4. Answer the following questions:

 

1. How many stages do amplifiers include?

2. What are the main parts of a three-stage amplifier?

3. By what means are the grids of the tubes insulated?

4. What type of grid bias is employed?

5. In what way is the voltage variation transferred?