SU1520580A1 - Erasure generator - Google Patents

Abstract

The invention relates to the field of radio engineering and can be used in tape recorders with an autonomous power source. The purpose of the invention is to increase the efficiency and current erasure. The generator contains transistors 1 and 2 of different types of conductivity, magnetic head 3, three capacitors 4-6, an additional transistor 7, resistors 8 and 9 connected in a certain way. The use of a generator in a bridge circuit can significantly reduce the supply voltage. 2 Il.

Description

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The invention relates to radio engineering and can be used in household tape recorders with autonomous power sources.

. The aim of the invention is to increase K11D and increase erase current.

Fig "1 presents the generator circuit; Fig. 2 is a diagram illustrating an example of the application of a generator in a bridge circuit, allowing a significant reduction in the supply voltage of

The generator contains transistors 1 and 2 of different types of conductivity, the collectors of which are connected to each other, and the emitters are connected to the power supply bus and the common bus according to the normal polarity of their supply voltage. One of the outputs of the erasing head 3 is connected to a common bus, the other through the first capacitor 4 is connected to the connection point of the collectors of transistors

1 and 2 and through the second and third feedback capacitors 5 and 6 to the bases of transistors 1 and 2, respectively, the base of transistor 1 is connected to the collector of the additionally introduced transistor 7, and through a resistor 8 to the base of transistor 7, the base of transistor

2 connected to the emitter of the transistor 7 and through a resistor 9 - with the base of the transistor 7 o

The erase generator works as follows

When the supply voltage is applied through the bases of transistors 1 and 2, current 1 flows (G, the value of which is approximately determined by the expression

t a

 RS RS

where is the power supply voltage; Uj-, - open voltage

transistors I and 2, respectively;

RJ, Rg - resistors 8 and 9, respectively.

The effect of transistor 7 at this moment is neglected, since the magnitudes

0

five

Q

0

five

five

resistors 8 and 9 are taken such that equality

IfRg Us ,,,

where and is the opening voltage of the transistor 7 "

The presence of the base current of transistors 1 and 2 means their active amplifying mode, therefore the erase generator is included in the continuous oscillation mode, which is maintained by currents flowing through the capacitors 5 and 6 and through the base-emitter transitions of the transistors 2

The greatest reduction in supply voltage can be achieved when using a generator in a bridge circuit (Fig 2). To maintain the frequency of the generator and optimally match its transistors with the capacitance circuit in the bridge circuit, they must be doubled.

Claims (1)

Formula image shadow The erasure generator containing two bipolar transistors of different conductivity type, the collectors of which are interconnected and, through the first capacitors, the winding of the erase magnetic head with a common bus, the bases of the transistors are interconnected via two series-connected resistors and connected respectively through the second and third capacitors to the output of a capacitor connected to the output winding of the erase magnetic head, and the emitters of the transistors are connected respectively to the power bus and the common shield, so that, in order to increase the efficiency and increase the erase current, a third transistor is connected to it, connected by a collector and emitter to the bases of the first and second transistors, respectively, and the base is connected to the junction point of the first and second resistors . UHI / 3 Hh F {1B.1