JPS58139073A - Oscilloscope - Google Patents

Abstract

PURPOSE:To conserve the power consumption of the power source by varying the resistance value of a variable resistance circuit inserted into a power source circuit of a power amplifier according to the selection of a swith for limiting band. CONSTITUTION:When a switch SW2 is turned to the position for bypassing a low pass filter LPF, a resistor R4 is selected and when it is turned to the position of the low pass filter LPF, a resistor 5 is selected while the resistance value of the resistor R4 is set at a value lower than that of the resistor 5. With such an arrangement, when the band is not limited, the power is amplified in a better linearity to a high pass frequency where deflection electrodes P1 and P2 give a low impedance. When the limiting of the band is performed, current energizing a transistor Q1 decreases to save the power consumption of the power source. This can achieve the conservation of the power consumption of the power source.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in an oscilloscope equipped with a changeover switch for limiting the frequency band of an observation signal.

FIG. 1 is a block diagram of the main parts of a conventional oscilloscope, in which the observation signal applied to the input IN is inserted into an attenuator ATT or bypassed via a switch 8Wl depending on the level of the observation signal. (pre-amplifier) is given to IA,
After being amplified in this, the low-frequency e-wave JLPF for band limiting is applied depending on the observation conditions, or it is fed to the power amplifier PA via the switch 8Ws for band limiting switching, which bypasses it. After reaching the specified power by
The voltage is applied between the deflection electrodes Pl and Pg of the cathode ray tube.

Note that there is capacitance between the deflection electrodes Pl and Pa, and the load impedance of the power amplifier PA is capacitive.
Since the load impedance of the power amplifier FA decreases,
The operating point of is set to a relatively large current flow value so that sufficient amplitude can be obtained even at low load impedance.

For this reason, the switch SW 11 is connected to a low-frequency f-wave device LPFIM.
Even when the power amplifier PA4C is switched to MLJ limit and the power amplifier PA4C is switched to MLJ limit, a relatively large current flows through the power amplifier PA4C, which consumes a large amount of power. This has the disadvantage of shortening its lifespan.

The present invention has the purpose of fundamentally eliminating the above-mentioned drawbacks of the conventional power amplifier. A resistor (b) path is inserted into the J-ro Hachimachi bend, and the resistance value of the variable resistance circuit is changed according to the switching of the band limit switch, thereby reducing the current flowing through the power amplifier during band limit. This provides an extremely effective oscilloscope.

Hereinafter, the present invention will be explained in detail with reference to FIG. 2 and subsequent figures showing embodiments.

Fig. 2 is a block diagram similar to Fig. 1, but a variable resistance circuit VRC is inserted and provided on the power supply E side of one power amplifier). The resistance value of the resistor changes.

Figure 3 is a circuit diagram showing a specific example of the power amplifier PA and the variable resistance circuit RC. A power amplifier PA is configured, while a resistor Rs is inserted in series to the emitter of the transistor Q"s, a resistor R@ is inserted between the emitter and base of the transistor Qs, and a switch 8Ws is used. A variable resistance circuit VRC is configured by resistors R4, R11, etc. that are selectively connected between the base of the transistor Qs and the common circuit, and the base bias of the transistor Qs changes according to switching of the switch 8Ws. Accordingly, the emitter-collector resistance of the transistor Qs changes.

That is, when the switch 8Wm is switched to the low frequency r-wavelength filter LPF, the resistor R4 is selected, and
When the switch 8Ws is switched to the low-frequency f-wave generator LPFil, the resistor Ri is selected and the resistance value of the resistor R4 is set to a lower value than the resistance value of the resistor R6. Therefore, if resistor R4 is selected, the forward bias of transistor Qs increases, and transistor Q
Since the emitter-collector resistance of 1 is reduced, the transistor Ql is connected via the resistor R1 and the transistor Qs.
The current flowing through the current increases, and the operating point of this
.

direction of load impedance.

On the other hand, if resistor Ri is selected, transistor Qs
Since the forward bias of the transistor Qs decreases and the emitter-collector resistance of the transistor Qs increases, the current passing through the transistor Ql decreases, and its operating point becomes oriented towards high load impedance.

Therefore, when band-limiting is not performed, dynamic power amplification is performed with good linearity up to high frequencies where the deflection electrodes PI and PI exhibit low impedance, while when band-limiting is performed, the The current flowing through Ql is reduced, the power consumption of the power supply is reduced, and the stain force is amplified with sufficient linearity up to a predetermined frequency.

However, the single-force pedal width device PAK may use a single-end push-pull circuit, etc., and the configuration of the variable resistance circuit RC can be arbitrarily selected according to the conditions, and the present invention can be modified in various ways. It is free.

As is clear from the above explanation, according to the present invention, if the frequency band of the observation signal is limited, the current consumption of the power amplifier is reduced at the same time. A remarkable effect can be obtained on the oscilloscope.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of main parts showing a conventional example, FIG. 2 is a block diagram similar to FIG. 1 showing an embodiment of the present invention, and FIG. 3 is a concrete diagram of the power amplifier and variable resistance circuit in FIG. FIG. 2 is a circuit diagram showing an example. PA...Power amplifier, vRC...Variable resistance circuit, 8Ws...Φ switch, Ql, Qml...Transistor, R1-R1...Resistor, E...Fist power supply. Patent Applicant Hitachi Electronics Co., Ltd. Agent Masa Yamayo & (1 other person) Utsu 1 Ward “399-

Claims (1)

[Claims] In an oscilloscope having a switch for switching band limit, a variable resistance circuit is provided, the resistance value of which changes according to the switching of a 1tII switch inserted into a power supply circuit of a power amplifier, thereby varying the current flowing through the power amplifier. An oscilloscope featuring: