JPH04181506A - Ic for magnetic card reader - Google Patents

Abstract

PURPOSE:To obtain a uniform read characteristic over a wide range of input signal frequencies by providing an automatic gain adjusting circuit which detects the amplitude of an input signal and adjusts the gain of an internal circuit. CONSTITUTION:An amplifier circuit 1a amplifies a signal from an input read head H and feeds the signal to a peak sensing circuit P1 at the next stage. The circuit P1 detects a peak of the output signal from the circuit A1 along with an external resistor R and capacitors C1, C2. The signal after the peak detection is processed in an operating circuit M1 at the next stage and output as a final output signal from a terminal 6. An automatic gain adjusting circuit AGC detects the amplitude of the input signal thereby to adjust the gain of the circuits A1, P1. Although the amplitude of the signal from the head H is generally larger when the frequency is higher, the amplitude of the waveform at a terminal 3 becomes approximately uniform because of the presence of the circuit AGC.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to an IC for a magnetic card reader.

[Prior Art 1] A block diagram of a conventional magnetic card reader IC is shown in FIG. 3. In FIG. (1
) to (6) are IC terminals, (H) is the reading head,
(CI) and (C2) are external capacitors, and (R1 is an external resistor. Figure 4 is a waveform diagram showing the operation of the (3) terminal of the magnetic card reader IC in Figure 3. be.

Next, the operation will be explained. In Fig. 3, the amplifier circuit (Al) amplifies the signal from the input reading head, and sends it to the next stage peak sense circuit (Pl). Capacitor (
0, 1), (C2>), performs peak detection of the output signal - signal of the amplifier circuit (A1). After detecting the peak, the 9 signal is subjected to calculation processing in the next calculation circuit C-1), and the final output signal is It is output from terminal (6) as .

Here, the signal from the reading head (2) usually has a larger amplitude as the frequency is higher, as shown in Figure 4, and the signal at terminal (3) also has a waveform as shown in Figure 4. . Capacitor (CI), (C2), resistance can)
Since the external circuit consisting of can only be determined as one,
External circuit constants are determined by whether the input signal station wave number is higher or lower.

[Problem to be solved by the invention]

Since the conventional FII card reader IC was configured as described above, there was a problem in that it was not possible to obtain uniform reading characteristics over a wide range of input signal frequencies. The purpose of this system is to obtain uniform reading characteristics over a wide range of input signal station wave numbers even with only one external circuit.

[Means to solve the problem] The magnetic card reader IC according to the present invention is as follows.

It is equipped with a gain adjustment circuit that detects the amplitude of the input signal and adjusts the gain of the internal circuit according to the amplitude.

[Function] The gain adjustment circuit according to the present invention detects the amplitude of the input signal and adjusts the gains of the amplifier circuit and the peak sense circuit according to the amplitude.

I Example J Hereinafter, an example of the present invention will be described with reference to rotation pressure. $1
In the figure, (Al) shows the amplifier circuit, (PI) shows the peak sense circuit, (S1) shows the arithmetic circuit, and (AGC) shows the automatic gain adjustment circuit. Also, (1) to (6) show the terminals of the IC. , fEll is the reading head, (CI), (C2)
is an external capacitor, (R1 is an external resistor, and Figure 2 is the terminal of the magnetic card reader IC in Figure 1.
3) is a waveform diagram showing the operation of FIG.

Next, the operation will be explained. In Figure 1, the amplifier circuit (A1) amplifies the signal from the input reading head (field) and sends it to the next stage peak sense circuit (Pl).The peak sense circuit (Pl) has an external resistor (R). , capacitor (
The peak-to-lateral ratio of the output signal of the amplifier circuit (Al I) is performed together with CI) and (C2).The peak detected signal is subjected to arithmetic processing in the next arithmetic circuit (III), and is sent to the terminal (6) as the final output signal. ) to 8 points.Also, automatic gain -
! One circuit (AGC) detects the amplitude of the input signal and adjusts the gain of the amplifier circuit (Al + ) and the peak sense circuit (Pl).

Here, the signal from the reading head (as shown in Figure 4) is normally higher in frequency, higher in amplitude;
By providing an automatic gain control circuit (AGC), the waveform at the terminal (3) has a nearly constant tR width as shown in Figure 2, so 8 capacitors (CI), (
C2) The circuit can handle a wide range of input signal frequencies by externally attaching the l1g type consisting of a resistor can. [Effects of the Invention] As described above, according to the present invention, the amplitude of the input signal can be detected. Since it is equipped with an automatic gain adjustment circuit that adjusts the gain of the internal circuit, it is possible to obtain a signal with a constant amplitude regardless of the frequency of the input signal. Furthermore, by detecting the amplitude of the input signal and adjusting the gain of the internal circuit while the discard bit signal is being received, the gain of the internal circuit can be adjusted without the need for a gain adjustment signal. There are effects such as being able to.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an IC for a magnetic card reader which is an embodiment of the present invention, and FIG. 2 is a block diagram of the circuit shown in FIG.
) waveform diagram, Figure 3 is a conventional magnetic card reader IC.
FIG. 4 is a waveform diagram of the terminal (3) of the circuit of FIG. In the figure, (All is an amplifier circuit, (Pl) is a peak sense circuit, C&i1) is an arithmetic circuit, (AGC) is an automatic gain adjustment circuit, (1) to (6) are IC terminals, and (El) is a reading head. (C1) and (C2) are external capacitors, and the hammer is an external resistor. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] It is equipped with an input signal amplification circuit, a peak sense circuit that detects the peak value of the amplified signal, and an arithmetic circuit that calculates the peak sensed signal and outputs an output signal. An IC for a magnetic card reader, comprising an automatic gain adjustment circuit that adjusts and fixes the gain of an internal circuit accordingly.