CN215641355U

CN215641355U - Bipolar transistor low-frequency noise test fixture

Info

Publication number: CN215641355U
Application number: CN202022292044.XU
Authority: CN
Inventors: 何黎
Original assignee: Wuhan Gewuxin Technology Co ltd
Current assignee: Wuhan Gewuxin Technology Co ltd
Priority date: 2020-10-14
Filing date: 2020-10-14
Publication date: 2022-01-25
Anticipated expiration: 2030-10-14

Abstract

The utility model provides a bipolar transistor low-frequency noise test fixture which comprises a base, a shielding mechanism, a circuit board and a positioning frame. The circuit board is arranged in the base, and a test circuit for testing the bipolar transistor is arranged on the circuit board; the positioning frame is arranged on the circuit board and is used for installing a bipolar transistor to be tested; the shielding mechanism is arranged on the base and provides a space for shielding the interference signal of the test circuit and the external interference signal for the circuit board. Compared with the prior art, the test fixture provided by the utility model has the advantages that by arranging the shielding mechanism, the influence of external interference signals can be effectively reduced, and the accuracy of a detection result is improved; the pressing block is arranged to ensure that the bipolar transistor to be tested is in full contact with a connection point on the circuit board; by arranging the circuit board and the plug connector, the circuit connection is simple and rapid in the test process.

Description

Bipolar transistor low-frequency noise test fixture

Technical Field

The utility model relates to the technical field of low-frequency noise testing, in particular to a low-frequency noise testing clamp for a bipolar transistor.

Background

A bipolar transistor is a current control device consisting of two back-to-back PN junctions, with electrons and holes participating in conduction simultaneously to obtain voltage, current, or signal gain. In the three layers of semiconductors formed inside, the middle layer is called a base region, and the two outer layers are respectively called an emitter region and a collector region.

The bipolar transistor has good linearity, noise characteristics, current driving capability, and excellent matching characteristics. They have important applications in analog circuits and hybrid integrated circuits, and comparators, operational amplifiers, integrated voltage regulators and the like formed by the circuits are widely applied to spaceflight satellite-borne equipment and weaponry.

The noise of bipolar transistors is generally classified into four categories by physical source: thermal noise, shot noise, distribution noise, and 1/f noise. Thermal noise is a current fluctuation caused by irregular thermal motion of carriers on the base region of a transistor or various resistors, and is also called white noise because the frequency spectrum of the thermal noise is uniform. Shot noise is a minute fluctuation in current caused when carriers pass through the potential barrier region unevenly. Distributed noise is I caused by the random recombination process of carriers in the base region_B、I_CThe distribution ratio varies the generated noise. 1/f noise in the transistor noise spectrum, the noise rises sharply at low frequencies, is inversely proportional to frequency, is primarily caused by poor device surface cleaning or internal defects, and is related to the purity of the semiconductor material. The distribution noise and the 1/f noise can well reflect the imperfection of the device, thereby representing the quality and reliability of the device.

Compared with the traditional reliability evaluation method, the low-frequency noise test of the bipolar transistor has the advantages of no damage to devices, direct test results, quick test process and the like, and is an important index in reliability evaluation and screening.

As shown in FIG. 1, when testing low-frequency noise of a bipolar transistor, R is_bIs a source resistance, R_cFor bias resistance, the white noise source is the excitation source of 200 bipolar transistor test, and passes through the source resistor R_bThe current or voltage of the base electrode is adjusted by inputting the current or voltage to the bipolar transistor 4, so that the bipolar transistor 4 reaches a specific noise test set state. The CE terminal of the transistor is used as a noise output terminal, and performs appropriate signal amplification through the low-noise preamplifier 400, and is connected to the low-frequency noise test system 500.

However, when the bipolar transistor is tested for low-frequency noise, an interference signal is often generated, which affects the detection result.

SUMMERY OF THE UTILITY MODEL

Aiming at the defect that the detection result is influenced by the interference signal when the low-frequency noise test of the bipolar transistor is carried out in the prior art, the utility model aims to provide the low-frequency noise test fixture of the bipolar transistor, which plays the roles of positioning a to-be-tested piece, mechanically connecting, shielding interference, supplying direct current, protecting the to-be-tested piece and the low-frequency noise test in the low-frequency noise level test of the bipolar transistor, can effectively reduce the influence of the interference signal and improve the accuracy of the detection result.

The utility model also provides a bipolar transistor low-frequency noise test fixture, which comprises:

a base;

the circuit board is arranged in the base, and a test circuit for testing the bipolar transistor is arranged on the circuit board;

the positioning frame is arranged on the circuit board and used for mounting a bipolar transistor to be tested;

and the shielding mechanism is arranged on the base and provides a space for shielding the interference signal of the test circuit and the external interference signal for the circuit board.

Preferably, the test circuit includes: the white noise control circuit comprises a bias circuit, a white noise input circuit and an output circuit;

the bias circuit is used for providing direct-current voltage for the bipolar transistor to be tested;

the white noise input circuit is used for providing an excitation source for the bipolar transistor to be tested;

and the output circuit is used for transmitting the low-frequency noise of the bipolar transistor to be tested to the low-noise preamplifier.

Preferably, the circuit board is provided with ground through holes on both sides of the bias circuit, the white noise input circuit and the output circuit, and the ground through holes are grounded through the base.

Preferably, a connector connected with the test circuit is arranged on the base.

Preferably, the socket connector is a contact radio frequency connector.

Preferably, the positioning frame is provided with a mounting through hole, and the mounting through hole is used for accommodating a bipolar transistor to be tested.

Preferably, the shielding mechanism comprises a cover body, and the cover body is buckled on the base and forms a closed space with the base.

Preferably, a pressing block is arranged on the inner side face of the cover body, the pressing block is provided with a protruding part which can stretch into the mounting through hole, and the protruding part is in compression joint with the upper surface of the bipolar transistor to be tested.

Preferably, the base and the cover are both made of brass.

Preferably, the positioning frame is made of a plastic material.

Compared with the prior art, the test fixture provided by the utility model has the functions of positioning a to-be-tested piece, connecting a circuit, mechanically fixing, shielding an interference signal, supplying direct current, protecting the to-be-tested piece and testing low-frequency noise in the low-frequency noise level test of the bipolar transistor. By arranging the shielding mechanism, the influence of external interference signals can be effectively reduced, and the accuracy of a detection result is improved; the contact surfaces of the cover body and the base are subjected to smoothing treatment to enable the two contact surfaces to become smooth surfaces, so that the shielding capability of the cover is improved; by arranging the pressing block, when the cover body is buckled with the base, the pressing block is pressed right above the bipolar transistor to be tested, so that the bipolar transistor to be tested is ensured to be fully contacted with a connecting point on the circuit board; the positioning frame is made of plastic materials, and the bipolar transistor to be tested is further ensured to be fully contacted with the circuit board; by arranging the circuit board and the plug connector, the circuit connection is simple and rapid in the test process.

The features mentioned above can be combined in various suitable ways or replaced by equivalent features as long as the object of the utility model is achieved.

Drawings

The utility model will be described in more detail hereinafter on the basis of non-limiting examples only and with reference to the accompanying drawings. Wherein:

FIG. 1 is a circuit diagram of a bipolar transistor under test for low frequency noise;

FIG. 2 is an exploded view of a bipolar transistor low frequency noise test fixture according to an embodiment of the present invention;

fig. 3 is a schematic structural diagram of a fastening-state low-frequency noise test fixture for a bipolar transistor according to an embodiment of the present invention;

fig. 4 is a schematic structural diagram of a base according to an embodiment of the present invention;

fig. 5 is a schematic structural diagram of a cover according to an embodiment of the present invention;

fig. 6 is a schematic structural diagram of a circuit board according to an embodiment of the present invention;

fig. 7 is a schematic structural diagram of a positioning frame according to an embodiment of the present invention;

FIG. 8 is a schematic structural diagram of a pressure block according to an embodiment of the present invention;

FIG. 9 is a schematic view of a connector according to one embodiment of the present invention;

FIG. 10 is a schematic structural diagram of a set screw according to an embodiment of the present invention;

fig. 11 is a block diagram showing the structure of a low-frequency noise test apparatus for a bipolar transistor.

Description of reference numerals:

1. a cover body; 2. briquetting; 3. a positioning frame; 4. a bipolar transistor; 5. a first connector; 6. a second connector; 7. a third connector; 8. a fourth connector; 9. a circuit board; 10. a base; 11. a set screw; 12. mounting holes; 13. a first positioning hole; 14. a second positioning hole; 15. a third positioning hole; 16. a fourth positioning hole; 17. a ground via; 18. a microstrip line; 19. a ground plane; 20. PCB insulation channel without copper cladding; 21. a bias circuit; 22. a white noise input circuit; 23. an output circuit; 24. mounting a through hole; 25. a projection; 26. a fifth positioning hole; 27. a connection point; r_cA bias resistor; r_bA source resistance; 100. a low noise voltage source; 200. a source of white noise; 300. testing the clamp; 400. a low noise preamplifier; 500. a low frequency noise test system; 600. and (4) shielding the chamber.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention clearer and more complete, the following technical solutions of the present invention will be described in detail, and all other embodiments obtained by a person of ordinary skill in the art without creative efforts based on the specific embodiments of the present invention belong to the protection scope of the present invention.

The utility model provides a bipolar transistor low-frequency noise test fixture which plays roles in sample positioning, circuit connection, mechanical fixation, interference signal shielding, direct current power supply, protection of a to-be-tested piece and low-frequency noise test in a bipolar transistor low-frequency noise level test.

As shown in fig. 2 and 3, the low-frequency noise test fixture (hereinafter referred to as a test fixture) for a bipolar transistor includes a base 10, a shielding mechanism, a circuit board 9, and a positioning frame 3. The circuit board 9 is arranged in the base 10, and the circuit board 9 is provided with a positioning frame 3 for mounting a bipolar transistor to be tested and a test circuit for testing the bipolar transistor; the shielding mechanism is arranged on the base 10, provides a space for shielding the interference signal of the test circuit and the external interference signal for the circuit board 9 to be tested, can effectively isolate the internal and external radiation signals, eliminates the interference of external noise on the internal circuit signal of the test fixture, and effectively reduces the influence of the interference signal on the test result.

In one embodiment, as shown in fig. 4 and 5, the shielding mechanism includes a cover 1, a base 10 and the cover 1 are both provided with grooves, the cover 1 is fastened on the base 10 and forms a closed space with the base 10, and the space is used for accommodating the circuit board 9, the positioning frame 3 and the bipolar transistor 4 to be tested; in order to further improve the shielding capability of the test fixture, the contact surface between the cover 1 and the base 10 may be smoothed so that both contact surfaces become smooth surfaces. A plurality of first positioning holes 13 for fixing the positioning frame 3 are formed on the bottom surface of the base 10; the side of the base 10 is further opened with a plurality of mounting holes 12 for mounting connectors. The base 10 and the cover 1 can be made of metal materials such as copper and aluminum, and in this embodiment, the cover 1 and the base 10 are preferably made of brass material with high density and good shielding effect.

In one embodiment, as shown in FIG. 6, the test circuit on the circuit board 9 includes a bias circuit 21, a white noise input circuit 22, and an output circuit 23. The bias circuit 21 is configured to provide a dc voltage to the bipolar transistor 4 to be tested; the output circuit 23 is used for transmitting the low-frequency noise of the bipolar transistor 4 to be tested to the low-noise preamplifier; the white noise input circuit 22 is used to provide a source of excitation to the bipolar transistor 4 under test. The bias circuit 21 is provided with a bias resistor R_cAn active resistor R is arranged on the white noise input circuit 22_bThe white noise source is the excitation source of the bipolar transistor 4 test and passes through the source resistor R_bTo a test bipolar transistor 4 to be tested. The circuit board 9 is preferably a Rogers 4350 nickel-plated gold plate. On the circuit board 9, the two sides of the bias circuit 21, the white noise input circuit 22 and the output circuit 23 are respectively and uniformly provided with the grounding through holes 17, and the grounding through holes 17 are grounded through the base 10 to realize the equal potential of the grounding plane 19 and ensure the good grounding loop. The signal lines on the circuit board 9 are microstrip lines 18, and the signal lines are isolated from the ground plane 19 through PCB insulation channels 20 which are not covered with copper. The circuit board 9 is provided with a second positioning hole 14 corresponding to the first positioning hole 13, and the second positioning hole 14 is a through holeAnd a through hole penetrating through the circuit board 9 and used for fixing the positioning frame 3.

In one embodiment, in order to facilitate the connection of the circuit board 9 with the low noise voltage source, the white noise source and the low noise preamplifier located outside the test fixture, the test fixture further comprises a plurality of connectors, the connectors are inserted into the mounting holes 12 on the side wall of the base 10, one end of each connector extending into the test fixture is electrically connected with the test circuit, and the other end located outside the test fixture is used for connecting with the corresponding test instrument outside the test fixture. Specifically, as shown in fig. 2 and 9, the test fixture includes a first connector 5, a second connector 6, a third connector 7 and a fourth connector 8, wherein the first connector 5 is used for connecting a low noise voltage source and a bias circuit 21, the second connector 6 is used for connecting a low noise voltage source and a white noise input circuit 22, the third connector 7 is used for connecting a white noise source and a white noise input circuit 22, and the fourth connector 8 is used for connecting a noise preamplifier and output circuit 23. The circuit board 9 is grounded to a test instrument other than the test fixture. The connector insert of the test circuit is preferably a contact radio frequency connector.

In one embodiment, as shown in fig. 7, the positioning frame 3 to be tested is an insulator, and is provided with a mounting through hole 24 adapted to the bipolar transistor 4 to be tested, the mounting through hole 24 is used for accommodating the bipolar transistor 4 to be tested, the positioning frame 3 around the mounting through hole 24 is further provided with a third positioning hole 15 corresponding to the second positioning hole 14, and the third positioning hole 15 is a through hole penetrating through the positioning frame 3. When assembling the test fixture, the positioning screws 11 are used to sequentially pass through the third positioning holes 15 on the positioning frame 3 and the second positioning holes 14 on the circuit board 9, and then the positioning screws 11 are screwed into the first positioning holes 13 on the base 10, so that the circuit board 9 and the positioning frame 3 are mounted on the base 10. Before the test is started, the bipolar transistor 4 to be tested needs to be fitted into the mounting through hole 24 so that the bipolar transistor 4 to be tested contacts the connection point 27 on the circuit board 9.

In one embodiment, a voltage block 2 may also be provided in order to ensure that the bipolar transistor 4 under test is in sufficient contact with the connection point 27 on the circuit board 9. Specifically, as shown in fig. 8, the pressing block 2 includes a bottom plate, a protruding portion 25 protruding into the mounting through hole 24 is disposed on the bottom plate, a plurality of fourth positioning holes 16 are further disposed on the bottom plate, a fifth positioning hole 26 corresponding to the fourth positioning hole 16 is disposed on the cover body 1, and the positioning screw 11 is used to pass through the fourth positioning hole 16 and screw into the fifth positioning hole 26, so as to fix the pressing plate on the inner side surface of the cover body 1. When the cover body 1 is buckled on the base 10, the protruding part 25 extends into the mounting through hole 24 to be pressed with the upper surface of the bipolar transistor 4 to be tested, and the positioning frame 3 is matched with the pressing block 2 to ensure that the bipolar transistor 4 to be tested is fully contacted with the connection point 27 on the circuit board 9. The positioning frame 3 is preferably made of plastic materials, so that the bipolar transistor 4 to be tested is further ensured to be fully contacted with the circuit board 9.

The test fixture provided by the utility model can be applied to a bipolar transistor low-frequency noise test device (hereinafter referred to as a test device), as shown in fig. 11, the test device comprises a low-noise voltage source 100, a white noise source 200, a low-noise preamplifier 400, a low-frequency noise test system 500 and the test fixture 300 provided by the utility model. The low-frequency noise test system 500 is mainly composed of an A/D data acquisition card, control and analysis software, a D/A waveform output card and the like. The low-noise voltage source 100 transmits a direct-current voltage to the bipolar transistor 4 to be tested through the test circuit, the white noise source 200 provides an excitation source for the bipolar transistor 4 to be tested through the test circuit, the low-frequency noise of the bipolar transistor 4 to be tested is transmitted to the low-noise preamplifier 400 through the output circuit 23, and the low-noise preamplifier 400 transmits an output signal to the low-frequency noise test system 500 through the magnetic shielding cable.

To avoid environmental noise and the impact of the test system on the test results, the entire test link is performed in the shielded room 600, and the low frequency noise test system 500 is tested outside the shielded room 600.

After the test system and the test link are connected, the bipolar transistor 4 to be tested is placed in the test fixture 300, and the bipolar transistor 4 is ensured to be in good contact with the fixture. Adjusting bias current, bias voltage and test frequency to proper conditions, and turning on a working power supply; and adjusting the bandwidth and the gain of the low-noise preamplifier 400, setting the sampling rate, the frequency spectrum resolution and the average frequency of the low-noise test system 500 of the output signal of the low-noise preamplifier 400 in the range of the low-noise test system 500, and starting to acquire data after the device works stably and data are not obviously abnormal, so as to finish the low-noise test analysis of the device to be tested.

Finally, it should be noted that: the above embodiments and examples are only used to illustrate the technical solution of the present invention, but not to limit the same; although the present invention has been described in detail with reference to the foregoing embodiments and examples, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments or examples may still be modified, or some of the technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments or examples of the present invention.

Claims

1. A bipolar transistor low frequency noise test fixture, comprising:

a base;

the positioning frame is arranged on the circuit board and used for mounting a bipolar transistor to be tested; and

2. A bipolar transistor low frequency noise test fixture as defined in claim 1, wherein said test circuit comprises: the white noise control circuit comprises a bias circuit, a white noise input circuit and an output circuit;

3. The clamp for testing the low frequency noise of the bipolar transistor according to claim 2, wherein grounding through holes are formed on the circuit board at two sides of the bias circuit, at two sides of the white noise input circuit and at two sides of the output circuit, and the grounding through holes are grounded through the base.

4. A bipolar transistor low frequency noise test fixture as claimed in any one of claims 1 to 3, wherein said base is provided with a connector for connecting said test circuitry.

5. The bipolar transistor low frequency noise test fixture of claim 4, wherein said connector is a contact radio frequency connector.

6. The clamp for testing the low-frequency noise of the bipolar transistor according to any one of claims 1 to 3, wherein a mounting through hole is formed in the positioning frame, and the mounting through hole is used for accommodating the bipolar transistor to be tested.

7. The clamp for testing low frequency noise of the bipolar transistor according to claim 6, wherein the shielding mechanism comprises a cover body, and the cover body is buckled on the base and forms a closed space with the base.

8. The clamp for testing the low-frequency noise of the bipolar transistor according to claim 7, wherein a pressing block is arranged on the inner side surface of the cover body, the pressing block is provided with a protruding part which can extend into the mounting through hole, and the protruding part is in pressure joint with the upper surface of the bipolar transistor to be tested.

9. The clamp of claim 7, wherein the base and the cover are made of brass.

10. The clamp for testing the low frequency noise of the bipolar transistor according to claim 7, wherein the positioning frame is made of a plastic material.