Alternating current and direct current mixed noise source device

By employing a two-stage transistor current amplification and inductor isolation design, the problems of high cost and large size of existing AC/DC hybrid noise source devices are solved, realizing a low-cost AC/DC hybrid noise source device that can effectively drive filters and other devices under test, meeting the driving requirements of AC signals.

CN121308683APending Publication Date: 2026-01-09EAST CHINA INST OF OPTOELECTRONICS INTEGRATEDDEVICE
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Patent Information

Application Number
CN202511276775.6
Authority / Receiving Office
CN · China
Patent Type
Applications(China)
Current Assignee / Owner
Filing Date
2025-09-08
Publication Date
2026-01-09

AI Technical Summary

Technical Problem

Existing AC/DC hybrid noise source devices are costly and bulky, and cannot effectively test the suppression effect of filters on AC signals.

Method used

The design employs a two-stage transistor current amplification, capacitive coupling, and inductive isolation. It achieves the mixing and isolation of AC and DC signals through an input coupling capacitor, a two-stage current amplifier, and an inductive isolation circuit. The structure is simple and the cost is low.

Benefits of technology

A low-cost AC/DC hybrid noise source device has been developed, which can effectively drive devices under test such as filters, meet the driving requirements of AC signals, and has a simple structure and is easy to use.

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Abstract

The invention relates to an alternating current and direct current mixed noise source device. An alternating current signal source VIN1 is connected with one end of a capacitor C1, and the other end of the capacitor C1 is connected with the common end of a resistor R1 and a resistor R2; one end of the input resistor R3 is connected with the common end of the resistor R1 and the resistor R2, the other end of the input resistor R3 is connected to the base electrode of the first-stage amplifier V1, the emitter electrode of the first-stage amplifier V1 is connected to the base electrode end of the second-stage amplifier V2, the emitter electrode of the second-stage amplifier V2 is connected with one end of the resistor R4, the other end of the resistor R4 is grounded, and the collector electrodes of the two stages of triodes are connected together and connected with VCC; the emitter of the secondary amplifier V2 is connected with one end of a coupling capacitor C2, and the other end of the coupling capacitor C2 is a mixed signal output end VIN2; an inductor L1 is connected between the VCC and the mixed signal output end VIN2, and a capacitor C3 is connected between the VCC and the GND. The circuit has the advantages that two-stage triode current amplification, capacitance coupling, inductance isolation and the like are designed, and the circuit is simple in structure, low in cost and convenient to use.
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Description

Technical Field

[0001] This invention relates to the field of signal processing technology, specifically to an AC / DC hybrid noise source device. Background Technology

[0002] Passive filters are used to filter and suppress high-frequency noise at the input or output of a power supply. However, the input signal of the filter is either a DC voltage signal or an AC voltage signal, both of which are added separately. When the two signals are mixed, the AC signal is often highly suppressed by the DC voltage signal. When the two are directly superimposed on the input of the filter, not only is the active AC signal potentially damaged, but the suppression of the AC signal by the power supply also makes it impossible to test and evaluate the filter's suppression effect on the AC signal. Generally, AC / DC mixed noise source devices use operational amplifiers, power amplifiers, isolators, etc., which are expensive to manufacture and large in size. Summary of the Invention

[0003] The purpose of this invention is to provide a low-cost AC / DC hybrid noise source device, which can be widely applied in the fields of signal processing technology and testing technology.

[0004] The technical solution adopted by this invention to solve its technical problem is:

[0005] An AC / DC hybrid noise source device includes: an input coupling capacitor C1 connected to an AC voltage source, static operating point setting resistors R1 and R2 for two-stage current amplifiers, an amplifier input resistor R3, a first-stage amplifier transistor V1 and a second-stage amplifier transistor V2, a load resistor R4 for the second-stage amplifier, an AC / DC coupling capacitor C2, and an AC signal isolation inductor L1.

[0006] One end of resistor R1 is connected to VCC, and the other end is connected to one end of resistor R2. The other end of resistor R2 is grounded. AC signal source VIN1 is connected to one end of capacitor C1, and the other end of capacitor C1 is connected to the common terminal of resistors R1 and R2.

[0007] One end of the input resistor R3 is connected to the common terminal of resistors R1 and R2, and the other end is connected to the base of the first-stage amplifier V1. The emitter of the first-stage amplifier V1 is connected to the base of the second-stage amplifier V2. The emitter of the second-stage amplifier V2 is connected to one end of resistor R4, and the other end of resistor R4 is grounded. The collectors of the two transistors are connected together and connected to VCC.

[0008] The emitter of the second-stage amplifier V2 is connected to one end of the coupling capacitor C2, and the other end of the coupling capacitor C2 is the mixed signal output terminal VIN2;

[0009] Connect inductor L1 between VCC and the mixed signal output terminal VIN2.

[0010] A further technical solution is to connect capacitor C3 between VCC and GND.

[0011] In this invention, the AC signal is input to a two-stage current amplifier via VIN1, capacitor C1, and resistor R3. The two-stage current amplifier is composed of resistors R1, R2, and R4, and transistors V1 and V2. The two-stage current amplifier amplifies the drive current of the input AC signal by several tens of times. Inductor L1 isolates the AC and DC signals, preventing the AC signal from being completely suppressed by the power supply VCC.

[0012] Finally, the amplified AC signal is mixed with the DC power supply VCC and input to VIN2 through the coupling capacitor C2. VIN2 is then input to the filter under test and other circuits under test.

[0013] The advantages of this invention are that it employs a two-stage transistor current amplification design, capacitive coupling, and inductive isolation, resulting in a simple structure, low cost, and ease of use. Attached Figure Description

[0014] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below:

[0015] Figure 1 This is the overall schematic diagram of the detection circuit;

[0016] Figure 2 This is a circuit diagram of a two-stage AC signal current amplifier;

[0017] Figure 3 This is a circuit diagram for AC / DC signal isolation. Detailed Implementation

[0018] like Figure 1 As shown, this invention provides an AC / DC hybrid noise source device circuit, including: an AC voltage input coupling capacitor C1, static operating point setting resistors R1 and R2 for two-stage current amplifiers, an amplifier input resistor R3, a first-stage amplifier transistor V1 and a second-stage amplifier transistor V2, a load resistor R4 for the two-stage amplifiers, an AC / DC coupling capacitor C2, and an AC signal isolation inductor L1. The input resistor R3 is connected to the base of the first-stage amplifier V1, the emitter of the first-stage amplifier V1 is connected to the base of the second-stage amplifier V2, the emitter of the second-stage amplifier V2 is connected to resistor R4, the collectors of the two transistors are connected together and connected to VCC, C3 is connected between VCC and GND to suppress power supply noise, the coupling capacitor C2 superimposes the amplified AC signal and DC signal onto VIN2, and the inductor L1 prevents the AC voltage signal from being suppressed by the DC voltage signal VCC.

[0019] VIN1 is the input terminal of the AC signal source, with a drive current of only about 10mA. After being amplified by two stages of current amplifiers, the drive current of the AC voltage signal can reach above the A level, which meets the requirements for driving the AC voltage signal to the filter and other devices under test. The amplified AC voltage signal is then mixed with the DC voltage signal VCC after passing through the DC blocking coupling capacitor C2, and then sent to the input terminal VIN2 of the filter and other devices under test.

[0020] Figure 2 It is a two-stage AC signal current amplifier circuit. Figure 2 In this circuit, VIN1 is the input terminal of the AC signal source. Through coupling capacitor C1, it is connected to the input resistor R3 of the current amplifier. Resistor R3 is connected to the base input terminal of the first-stage current amplifier V1. C1 is also connected to resistor R1 to VCC and resistor R2 to GND. The collectors of the first-stage current amplifier V1 and the second-stage current amplifier are connected together and to the VCC power supply. The emitter of the first-stage current amplifier V1 is connected to the base of the second-stage current amplifier V2. The emitter of the second-stage current amplifier is connected to resistor R4 to GND and also to DC blocking coupling capacitor C2.

[0021] Figure 3 This is a circuit diagram for AC / DC signal isolation. The amplified AC voltage signal is connected to the DC blocking coupling capacitor C2 to VIN2. Inductor L1 is connected between VCC and VIN2 to prevent the AC voltage signal from being suppressed by the DC power supply VCC. VIN2 is the input terminal of the filter under test and other devices. Capacitor C3 is the noise filtering capacitor for the power supply VCC.

[0022] Any connection method and connection relationship that is the same as the entire implementation of this patent is considered to be within the scope of infringement of this patent.

Claims

1. A hybrid AC / DC noise source device, characterized in that... include: The input coupling capacitor C1 is connected to the AC voltage source, the static operating point setting resistors R1 and R2 of the two-stage current amplifier, the amplifier input resistor R3, the first-stage amplifier transistor V1 and the second-stage amplifier transistor V2, the load resistor R4 of the second-stage amplifier, the AC / DC coupling capacitor C2, and the AC signal isolation inductor L1. One end of resistor R1 is connected to VCC, and the other end is connected to one end of resistor R2. The other end of resistor R2 is grounded. AC signal source VIN1 is connected to one end of capacitor C1, and the other end of capacitor C1 is connected to the common terminal of resistors R1 and R2. One end of the input resistor R3 is connected to the common terminal of resistors R1 and R2, and the other end is connected to the base of the first-stage amplifier V1. The emitter of the first-stage amplifier V1 is connected to the base of the second-stage amplifier V2. The emitter of the second-stage amplifier V2 is connected to one end of resistor R4, and the other end of resistor R4 is grounded. The collectors of the two transistors are connected together and connected to VCC. The emitter of the second-stage amplifier V2 is connected to one end of the coupling capacitor C2, and the other end of the coupling capacitor C2 is the mixed signal output terminal VIN2; Connect inductor L1 between VCC and the mixed signal output terminal VIN2.

2. The AC / DC hybrid noise source device circuit according to claim 1, characterized in that: Connect capacitor C3 between VCC and GND.