Current of rest of an intensifying cascade is called the current consumed by it in the absence of an entrance signal. Changing it, it is possible to make a cascade or economic, but bringing the increased distortions, or more precisely transferring a signal form, but consuming big power.
Instruction
1. In all cases for change of current of rest of a cascade change, depending on a type of a cascade, either current of base of the transistor, or shift tension on a lamp grid.
2. For creation of current of base of the transistor which is switched on according to the scheme with the general emitter use the resistor connecting base or to the feeding tire or with the collector. The second is more preferable in terms of thermostabilization. The resistor resistance, the current of base which more is slightly opening, so, and current of rest of a cascade is less. There are also other, more perfect schemes of thermostabilization of bipolar transistors assuming use of several resistors.
3. For creation of tension of shift of a lamp connect its operating grid to the general wire via the high-resistance resistor (its face value will not be required to be changed), and between the cathode and the general wire turn on the resistor by means of which shift tension will be regulated. Zashuntiruyte his condenser (if it electrolytic, include it plus to the cathode). The more resistance of the cathode resistor, the is more also the locking tension on a grid which is negative concerning the cathode (but not the general wire), and, respectively, current of rest of a cascade is less.
4. If the cascade is used for strengthening on alternating current, give on it an entrance signal via the condenser with very small leak not to break its mode on a direct current. Remove an output signal from loading also via the condenser.
5. Irrespective of whether the cascade is lamp or transistor, take the resistor setting current of rest, big resistance that this current was small in the beginning. Give on a cascade entrance via the condenser such signal that its distortions could be found easily on hearing or on the oscillograph screen. Remove an output signal also via the condenser, and give it, respectively, on the control amplifier or an oscillograph. In advance install the transistor on the heat sink.
6. Consistently with the load resistor turn on the milliamperemeter. Only after it give food on a cascade. Current of rest will be small, and distortions - big.
7. Every time previously powering off a cascade, put in it the resistor of the lesser and smaller resistance. Current of rest will increase distortions - to decrease. When they cease to fall, stop reducing resistance. Do not try to learn in practice what will be at its further reduction - believe naslovo: strengthening will begin to fall, current of rest will increase up to unacceptably great value, the active element can fail.
8. If you accept the increased energy consumption of a cascade, leave rest current at the posinelny level and if you want to offer for the sake of profitability quality of strengthening, reduce rest current to desirable level.