JPS6213262Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an improvement of a nonlinear pre-emphasis circuit.

FIG. 1 shows a nonlinear pre-emphasis circuit of a conventional magnetic recording/reproducing device. In the figure 1,
2, 3, 8 are resistors, 4, 5 are capacitors, 6, 7
is a diode. The input signal enters from the input terminal A, and the low frequency component passes through the resistor 2, and the high frequency component passes through the resistor 3 and the high frequency enhancement capacitor 4 before proceeding to the next stage. By appropriately selecting the ratio of the resistors 2 and 3, the high frequency component can have a gain compared to the low frequency component. Next, the amplitude of the high frequency component is limited by the low frequency shedding capacitor 5 and the diodes 6 and 7, and an output signal is output to the output terminal B. In this way, by giving a relative gain to the high frequency components of the input signal and limiting the amplitude, a non-linear pre-emphasis circuit is constructed that increases the gain of the high frequency components relative to the low frequency components as the input signal becomes smaller. ing. Figure 2 shows the VHS standard characteristics of nonlinear pre-emphasis in a VTR.

However, when converting this circuit into an IC, even though the input and output terminals are connected within the IC, there are two capacitors 4 and 5, so at least three IC pins are required, and even though the circuit configuration is simple, However, there were disadvantages in that the number of IC output pins increased and that at least two capacitors had to be external components.

The present invention was made to eliminate the drawbacks of the conventional ones as described above, and it is possible to integrate the function of a capacitor used for cutting off the low frequency range of an amplitude limiting diode into a voltage generator that can be integrated. The purpose of the high-frequency enhancement capacitor is to provide a nonlinear pre-emphasis circuit that can be used with one end grounded, reducing the number of pins and external components when integrated.

FIG. 3 shows an embodiment of the nonlinear pre-emphasis circuit of the present invention.

In the figure 8, 9, 10, 12, 13, 18,
20, 25, 26, 27 are resistors, 14, 15 are diodes, 11, 16, 21, 23, 24 are transistors, 17, 22 are constant current sources, and 19 is a capacitor.

The input signal applied to input terminal A' is applied to the bases of transistors 11, 16, and 21. The collector voltage of the transistor 21 is the constant current source 22.
Since it is pulled by , it becomes a constant potential. On the other hand, the signal applied to the transistor 16 is subjected to emitter peaking by a resistor 18 and a capacitor 19, giving a gain to the high frequency component, and only the high frequency component is output to the collector of the transistor 16.

Further, clippers of diodes 14 and 15 are connected between the transistor 16 and the transistor 21 to limit the amplitude in the high range.

This high frequency component is mixed with the overall amplified signal in the MIX circuit of transistors 23 and 24.

That is, an output signal can be obtained at the output terminal B' in which the high frequency component has a gain, and the gain of the high frequency component increases with respect to the low frequency component as the input signal level decreases. By selecting the specifications, for example, characteristics of the VHS standard as shown in FIG. 2 can be obtained.

Other embodiments are shown in FIGS. 4, 5, and 6.

28, 32, 3 in Figures 4 to 6
6, 37, 38, 42, 45, 46, 50, 5
3, 56, 59, 61 are resistances, 29, 34, 35
is a diode, 31, 40, 44, 52, 55 are constant current sources, 33, 47, 57 are capacitors, 3
0, 39, 41, 43, 48, 49, 51, 5
4, 58, and 60 are transistors.

FIG. 4 shows an actual circuit inside the IC of section C shown in FIG. 3, and FIG. 5 shows an example in which transistors are used instead of diodes.

FIG. 6 shows another embodiment of the D section MIX circuit shown in FIG.

In addition, in FIG. 3, the full range amplifier is made up of resistors 10 and 12 and the transistor 11, and the high range amplifier is made up of resistors 13 and 18.
The emitter peaking circuit includes a transistor 16, a constant current source 17, and a capacitor 19. The clip circuit includes diodes 14 and 15, the high-frequency amplifier operating point circuit includes a resistor 20, a transistor 21, a constant current source 22, and the adder includes transistors 23 and 24. resistance 2
It consists of 5, 26, and 27.

Here, by changing the operation of the conventional low-frequency cutoff capacitor 5 to a high-frequency amplifier operating point circuit, the 2-pin,
By using a high-frequency amplifier instead of the high-frequency enhancement capacitor 4, the number of pins can be reduced to 1 pin and a total of 3 pins.

As described above, the conventional circuit uses two capacitors as shown in FIG. 1, but in the present invention, the same characteristics as the conventional circuit can be obtained with one capacitor. For this reason, when converting this circuit into an IC, what would have required three pins if the input/output pins were connected to other circuits inside the IC can now be realized with one pin. This has the effect of reducing the number of IC pins and reducing the number of IC pins.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of a conventional non-linear pre-emphasis circuit, Figure 2 is a VHS standard characteristic diagram of a non-linear pre-emphasis circuit in a VTR, and Figure 3 is an example of the non-linear pre-emphasis circuit of the present invention. The circuit diagrams shown in FIGS. 4 to 6 are circuit diagrams of other embodiments of the present invention. In the figure, 8, 9, 10, 12, 13, 1
8, 20, 21, 22 are resistors, 14, 15 are diodes, 11, 16, 21, 23, 24 are transistors, 17, 22 are constant current sources, 19 is a capacitor, A' is an input terminal, B' is an output It is a terminal.

Claims (1)

[Scope of utility model registration request] a full range amplifier, a high range amplifier, a voltage generation means, an output adder of the whole range amplifier and the high range amplifier, and when a potential difference between the output of the voltage generation means and the output of the high range amplifier reaches a predetermined level; A non-linear pre-emphasis circuit comprising bidirectional clipping means for clipping the output of the high-frequency amplifier, the voltage difference between the output of the voltage generating means and the operating point of the high-frequency amplifier being set below the operating level of the clipping means.