The amplifier has a stock on strengthening 6db, it is necessary in order that in case of deterioration, owing to any reasons, parameters of separate elements the coefficient of transfer of the amplifier did not fall below the set level determined by the specification.
As VCh of correction I chose the intercascade correcting chain of the 3rd order. But after calculation of coefficient of strengthening of the output cascade it appeared that the cascade gives too small strengthening, namely – about 5 dB. After calculation of the intermediate cascade approximately same results were received. As a result the general strengthening which is given out by cascades of the amplifier came out equal about 11 dB, instead of 15 demanded. For increase in coefficient of strengthening the third cascade on the KT916A transistor was replaced with the cascade with the addition of tension executed on the KT948B transistor. For an active element of the intermediate cascade the KT913B transistor was chosen.
As the cascade with addition of tension carries out raising of AChH, i.e. improves its form, we will consider that the cascade does not bring linear distortions and does not demand MKTs. Then we will make recalculation of distortions: We will give 2 dB on the intermediate cascade and 1 dB on the entrance.
What not to put the additional power supply subsequently, we will take too tension in a working point, as in other cascades. Current will be equal in a working point to the current of a collector of the transistor of the intermediate cascade divided into coefficient of strengthening of the intermediate cascade (in times) and increased on Then we receive the following coordinates of a working point:
The BOOM has to have the small level of nonlinear distortions and high efficiency, provide the set output power in a wide strip of frequencies and the uniform amplitude-frequency characteristic of a nonlinear locator.
At calculation of the demanded mode of the transistor intermediate and entrance cascades on a direct current, it is necessary to be guided by the ratios given in point 1 taking into account that it is replaced with the entrance resistance of the subsequent cascade. As the output cascade is the cascade with addition of tension, coordinate of a working point at the intermediate cascade the same, as at day off.
As the cascade with addition of tension was used, there was a shift of the working point calculated earlier. Tension will be equal in a working point of the KT948B transistor 12 volts. Current remains invariable, i.e. will be equal 5 amperes. It is also possible to change power supply face value - to take it equal 12 volts.
The size of inductance of a throttle gets out so that the variable component of current was not grounded via the power supply, and the size of blocking capacity – so that the collector of the VT1 transistor on alternating current was grounded.