JPH03225605A - Peak holding circuit - Google Patents

Abstract

PURPOSE:To obtain the circuit which is not changed in characteristic value by a frequencies by switching the current value with a constant current source by the frequency of an input signal. CONSTITUTION:A signal 21 of a positive polarity which is a reading out signal s inputted to the positive terminal of a comparator 1 and a peak holding signal 23 is inputted to the negative terminal. On the other hand, a signal 22 of a negative polarity which is a reading out signal is inputted to the positive terminal of a compara tor 2 and a peak holding signal 23 is inputted to the negative terminal. The outputs of both the comparators 1, 2 turn to an L when the potential of the negative terminal falls to the potential lower than the potential of the positive terminal. The outputs turn to an H when the above-mentioned potential attains a high potential. The output of the comparator 1 is inputted to the base of a transistor 3 and the output of the comparator 2 is inputted to the base of a transistor 4. The TRs 3,4 turn off when the outputs of the comparators 1, 2 turn to the H. The TRs turn off when the outupts turn to the L. A switch 9 turns on and the current value by the constant current source 5 increases when the frequency of the reading out signal 23 is 2F. The switch 9 turns off and the current value by the constant current source 5 decreases when the frequency is 1F.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a peak hold circuit for use in testing the output resolution characteristics of a read waveform of a magnetic disk device and for holding the peak value of an analog waveform.

[Conventional technology]

FIG. 2 is a circuit diagram showing an example of a conventional peak hold circuit, and FIG. 4 is a waveform diagram showing the waveform of a peak hold signal in the example of FIG.

A conventional peak hold circuit used for inspecting the output resolution characteristics of a read signal of a magnetic disk drive and for holding the peak value of an analog waveform includes two comparators 11 and 11, as shown in FIGS. 2 and 4. 12, two transistors 13 and 14 that are turned on and off by the outputs of the comparators 11 and 12, and a peak hold capacitor (capacitor) 16, so that the output of the comparator 11 is at a high level ( When the voltage becomes "H", the transistor 13 is turned on and the capacitor 16 is charged. Furthermore, even if the output of the comparator 12 becomes "Ho", the transistor 14 is turned on and the capacitor 16 is charged. When the comparators 11 and 12 both become low level ("L"), the transistors 13 and 14 are both turned off. Therefore, capacitor 16
is discharged through the resistor 17. FIG. 4 is a waveform diagram showing the waveform of the peak hold signal 33 in the example of FIG.
) is the waveform when the input signal frequency is low, (b)
shows the waveform when the frequency of the input signal is high.

[Problem to be solved by the invention]

The conventional peak hold circuit described above does not include a constant current source, and therefore has the disadvantage that the charging current changes due to fluctuations in temperature and voltage. Further, since the discharge is a trickle type that discharges through a resistor, there is also a drawback that the amount of discharge varies depending on the frequency of the read signal.

[Means to solve the problem]

The peak hold circuit of the present invention includes a first comparator that inputs the positive polarity signal of the read signal and the peak hold signal and compares them, and inputs the negative polarity signal of the read signal and the peak hold signal. A current switch circuit having a second comparator for comparing them, a first transistor that performs an on/off operation according to the output of the first comparator, and a second transistor that performs an on/off operation according to the output of the second comparator. , a switch that performs an on/off operation depending on the frequency of a read signal, and a constant current source that changes a current value according to the operation of the switch.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

In FIG. 1, a positive polarity signal 21 of the readout signal is input to the positive terminal of the comparator 1, and a peak hold signal 23 is input to the negative terminal. On the other hand, the negative polarity signal 22 of the read signal is input to the positive terminal of the converter 2, and the peak hold signal 23 is input to the negative terminal. Comparator 1
and 2, when the potential of the negative terminal becomes lower than the potential of the positive terminal, the output becomes "L", and when the potential becomes high, the output becomes "Ho". The output of comparator 1 is connected to the base of transistor 3. The output of comparator 2 is input to the base of transistor 4. When the outputs of comparators 1 and 2 become "'H", transistors 3 and 4 are turned off, and when they become "L", they are turned on.

When the frequency of the input signal (readout signal) 23 having two types of frequencies (frequency 2F and IF) is 2F, the switch 9 is turned on and the current value from the constant current source 5 increases, and the frequency of the input signal 23 increases. When is IF, the switch 9 is turned off and the current value from the constant current source 5 becomes small.

FIG. 3 is a waveform diagram showing the waveform of the peak hold signal in the embodiment of FIG. 1, and (a) shows that the frequency of the input signal 23 is I
(b) shows the waveform when the input signal 23 has a frequency of 2.
The waveform at F is shown. In this way, the constant current source 5
By changing the current value according to the frequency of the input signal 23, the rate of decrease of the peak hold signal with respect to the peak value of the read signal becomes the same, and when testing the output resolution characteristics of the read signal (calculating the ratio of IF and 2F), Highly accurate data equivalent to inspection results obtained using a digitizing oscilloscope etc. can be obtained.

〔Effect of the invention〕

As explained above, the peak hold circuit of the present invention
By switching the current value of the constant current source depending on the frequency of the input signal, it is possible to obtain a circuit whose characteristic values do not change depending on the frequency.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is a circuit diagram showing an example of a conventional peak hold circuit, and FIG. 3 is a waveform showing the waveform of the peak hold signal in the embodiment of FIG. 4 are waveform diagrams showing the waveform of the peak hold signal in the example of FIG. 2. 1, 2, 11, 12... Comparator, 3, 4
13・14...Transistor, 5...
Constant current source, 6/16... Capacitor, 9...
...Switch, 17...Resistance.

Claims (1)

[Claims] 1. A first comparator that inputs a positive polarity signal of the readout signal and a peak hold signal and compares them; and a first comparator that inputs a negative polarity signal of the readout signal and the peak hold signal; A current having a second comparator for comparing them, a first transistor that is turned on and off by the output of the first comparator, and a second transistor that is turned on and off by the output of the second comparator. 1. A peak hold circuit comprising: a switch circuit; a switch that performs on/off operations depending on the frequency of a read signal; and a constant current source that switches a current value according to the operation of the switch. 2. A first comparator that inputs the positive polarity signal of the readout signal and the peak hold signal and compares them, and a second comparator that inputs the negative polarity signal of the readout signal and the peak hold signal and compares them. a current switch circuit comprising a comparator, a first transistor that is turned on and off by the output of the first comparator, and a second transistor that is turned on and off by the output of the second comparator; The present invention is characterized by comprising: a switch that performs on/off operations depending on the frequency of a readout signal having a frequency of peak hold circuit.