Test apparatus for measuring a characteristic of a device under test

• US 8,319,503 B2
• Filed: 11/16/2009
• Issued: 11/27/2012
• Est. Priority Date: 11/24/2008
• Status: Active Grant

• Current Assignee: FormFactor Incorporated
• Original Assignee: Cascade Microtech Incorporated (FormFactor Incorporated)
• Inventors: Negishi, Kazuki, Hansen, Mark
• Primary Examiner(s): Tang, Minh N
• Application Number:
  US12/590,955
• Publication Number:
  US 20100127714A1
• Time in Patent Office: 1,107 Days
• Field of Search: None
• US Class Current: 324/613
• CPC Class Codes: G01R 1/18 Screening arrangements against electric or magnetic fields, e.g. against earth's field
• CPC Class Codes: G01R 29/26 Measuring noise figure; Measuring signal-to-noise ratio

Abstract

A flicker noise test system includes a guarded signal path and an unguarded signal path selectively connectable to respective terminals of a device under test. The selected signal path is connectable a terminal without disconnecting cables or changing probes.

Claims

1. A test apparatus for measuring a characteristic of a device under test, said test apparatus comprising:

(a) a guarded first signal path conductively connected to a signal source and conductively connected to a terminal of said device under test; and

(b) an unguarded second signal path conductively connected to said signal source and conductively connected to said terminal of said device under test, said first signal path operative to conductively connect said signal source to said terminal without disconnecting portions of said second signal path from said signal source and said terminal and said second signal path operative to conductively connect said signal source to said terminal without disconnecting portions of said first signal path from said signal source and said terminal, wherein said second signal path includes a filter to exclude higher frequency components of a signal from said signal source, and further wherein said second signal path includes a plurality of resistors, each resistor of the plurality of resistors conductively interconnectable with said filter and said terminal by operation of a respective one of a plurality of switches.

2. The test apparatus of claim 1 further comprising:

(a) a first relay;

(b) a second relay operable with said first relay to interconnect said signal source and said terminal with one of a portion of said first signal path and a portion of said second signal path, interconnecting said signal source and said terminal with said portion of said first signal path disconnecting said portion of said second signal path from said signal source and said terminal and interconnecting said signal source and said terminal with said portion of said second signal path disconnecting said portion of said first signal path from said signal source and said terminal; and

(c) a third relay operable to connect a guard signal path to said signal source when said first signal path interconnects said signal source and said terminal and to disconnect said guard signal path from said signal source when said second signal path interconnects said signal source and said terminal, said guard signal path at least partially surrounding said first signal path for a substantial portion of a length of said first signal path between said signal source and said terminal.

3. The test apparatus of claim 2 wherein at least one of said first relay, said second relay and said third relay comprises a reed relay.

4. The test apparatus of claim 1 wherein said signal source comprises a source monitor unit.

5. The test apparatus of claim 1 wherein said signal source is a first signal source and said terminal is a first terminal, said test apparatus further comprising:

(a) a guarded third signal path conductively connected to a second signal source and conductively connected to a second terminal of said device under test; and

(b) an unguarded fourth signal path conductively connected to said second signal source and conductively connected to said second terminal of said device under test, said third signal path operative to conductively connect said second signal source to said second terminal without disconnecting portions of said fourth signal path from said second signal source and said second terminal and said fourth signal path operative to conductively connect said second signal source to said second terminal without disconnecting portions of said third signal path from said second signal source and said second terminal.

6. The test apparatus of claim 5 further comprising:

(a) a fourth relay;

(b) a fifth relay operable with said fourth relay to interconnect said second signal source and said second terminal with one of a portion of said third signal path and a portion of said fourth signal path, interconnecting said second signal source and said second terminal with said portion of said third signal path disconnecting said portion of said fourth signal path from said second signal source and said second terminal and interconnecting said second signal source and said second terminal with said portion of said fourth signal path disconnecting said portion of said third signal path from said second signal source and said second terminal; and

(c) a sixth relay operable to connect a second guard signal path to said second signal source when said third signal path interconnects said second signal source and said second terminal and to disconnect said second guard signal path from said second signal source when said fourth signal path interconnects said second signal source and said second terminal, said second guard signal path at least partially surrounding said third signal path for a substantial portion of a length of said third signal path between said second signal source and said second terminal.

7. The test apparatus of claim 5 wherein said fourth signal path includes a filter to exclude higher frequency components of a signal conducted between said second terminal and said second signal source.

8. The test apparatus of claim 5 wherein said second signal source comprises a second source monitor unit.

9. The test apparatus of claim 5, wherein:

(a) a guarded fifth signal path conductively connected to a third signal source and conductively connected to a third terminal of said device under test; and

(b) an unguarded sixth signal path conductively connected to said third signal source and conductively connected to said third terminal of said device under test, said fifth signal path operative to conductively connect said third signal source to said third terminal without disconnecting portions said sixth signal path from said third signal source and said third terminal and said sixth signal path operative to conductively connect said third signal source to said third terminal without disconnecting portions of said fifth signal path from said third signal source and said third terminal.

10. A test apparatus for measuring a characteristic of a device under test, said test apparatus comprising:

(a) a guarded first signal path conductively connected to a first signal source and conductively connected to a first terminal of said device under test;

(b) an unguarded second signal path conductively connected to said first signal source and conductively connected to said first terminal of said device under test, said first signal path operative to conductively connect said first signal source to said first terminal without disconnecting portions of said second signal path from said first signal source and said first terminal and said second signal path operative to conductively connect said first signal source to said first terminal without disconnecting portions of said first signal path from said first signal source and said first terminal;

(c) a guarded third signal path conductively connected to a second signal source and conductively connected to a second terminal of said device under test;

(d) an unguarded fourth signal path conductively connected to said second signal source and conductively connected to said second terminal of said device under test, said third signal path operative to conductively connect said second signal source to said second terminal without disconnecting portions of said fourth signal path from said second signal source and said second terminal and said fourth signal path operative to conductively connect said second signal source to said second terminal without disconnecting portions of said third signal path from said second signal source and said second terminal;

(e) a guarded fifth signal path conductively connected to a third signal source and conductively connected to a third terminal of said device under test; and

(f) an unguarded sixth signal path conductively connected to said third signal source and conductively connected to said third terminal of said device under test, said fifth signal path operative to conductively connect said third signal source to said third terminal without disconnecting portions of said sixth signal path from said third signal source and said third terminal and said sixth signal path operative to conductively connect said third signal source to said third terminal without disconnecting portions of said fifth signal path from said third signal source and said third terminal.

11. The test apparatus of claim 10 wherein said sixth signal path includes a filter to exclude higher frequency components of a signal from said third signal source.

12. The test apparatus of claim 11 wherein said sixth signal path further includes a resistor conductively connecting said filter and said third terminal.

13. The test apparatus of claim 11 wherein said sixth signal path includes a plurality of resistors, each resistor of the plurality of resistors conductively interconnectable with said filter and said third terminal by operation of a respective one of a plurality of switches.

14. The test apparatus of claim 13 further comprising:

(a) a low noise amplifier having an output and an input, which is connected to said sixth signal path between said individual resistor and said third terminal; and

(b) a test instrument connected to said output of said low noise amplifier.

15. The test apparatus of claim 10 further comprising:

(a) a seventh relay;

(b) a eighth relay operable with said seventh relay to interconnect said third signal source and said third terminal with one of a portion of said fifth signal path and a portion of said sixth signal path, interconnecting said third signal source and said third terminal with said portion of said fifth signal path disconnecting said portion of said sixth signal path from said third signal source and said third terminal and interconnecting said third signal source and said third terminal with said portion of said sixth signal path disconnecting said portion of said fifth signal path from said third signal source and said third terminal; and

(c) a ninth relay operable to connect a third guard signal path to said third signal source when said fifth signal path interconnects said third signal source and said third terminal and to disconnect said third guard signal path from said third signal source when said sixth signal path interconnects said third signal source and said third terminal, said third guard signal path at least partially surrounding said fifth signal path for a substantial portion of a length of said fifth signal path between said third signal source and said third terminal.

16. The test apparatus of claim 15 wherein a portion of said first, said second, said third, said fourth, said fifth and said sixth signal paths;

and said first, said second, said third, said fourth, said fifth, said sixth, said seventh, said eighth and said ninth relays and at least two resistors are secured to a holder of a probe having probe tips operable to connect said signal paths to the respective first, second and third terminals of said device under test.

17. The test apparatus of claim 10 wherein said third signal source comprises a third source monitor unit.

18. The test apparatus of claim 10 further comprising:

(a) a guarded seventh signal path conductively connected to a fourth signal source and conductively connected to a fourth terminal of said device under test; and

(b) an unguarded eighth signal path conductively connected to said fourth signal source and conductively connected to said fourth terminal of said device under test, said seventh signal path operative to conductively connect said fourth signal source to said fourth terminal without disconnecting portions of said eighth signal path from said fourth signal source and said fourth terminal and said fourth signal path operative to conductively connect said fourth signal source to said fourth terminal without disconnecting portions of said seventh signal path from said fourth signal source and said fourth terminal.

19. The test apparatus of claim 18 further comprising:

(a) a tenth relay;

(b) a eleventh relay operable with said tenth relay to interconnect said fourth signal source and said fourth terminal with one of a portion of said seventh signal path and a portion of said eighth signal path, interconnecting said fourth signal source and said fourth terminal with said portion of said seventh signal path disconnecting said portion of said eighth signal path from said fourth signal source and said fourth terminal and interconnecting said fourth signal source and said fourth terminal with said portion of said eighth signal path disconnecting said portion of said seventh signal path from said fourth signal source and said fourth terminal; and

(c) a twelfth relay operable to connect a fourth guard signal path to said fourth signal source when said seventh signal path interconnects said fourth signal source and said fourth terminal and to disconnect said fourth guard signal path from said fourth signal source when said eighth signal path interconnects said fourth signal source and said fourth terminal, said fourth guard signal path at least partially surrounding said seventh signal path for a substantial portion of a length of said seventh signal path between said fourth signal source and said fourth terminal.

20. The test apparatus of claim 19 wherein said eighth signal path includes a filter to exclude higher frequency components of a signal conducted between said fourth terminal and said fourth signal source.

21. The test apparatus of claim 19 wherein said fourth signal source comprises a fourth source monitor unit.

22. The test apparatus of claim 10, wherein said second signal path includes a filter to exclude higher frequency components of a signal from said first signal source.

23. The test apparatus of claim 22, wherein said second signal path includes a plurality of resistors, each resistor of the plurality of resistors conductively interconnectable with said filter and said first terminal by operation of a selected one of a plurality of switches.