Exhibit 31.2

CERTIFICATIONS

I,
William M. Clancy, certify that:

|1. | I have reviewed this
  quarterly report on Form 10-Q of Siliconix incorporated;                                                                                                                                                                                                                                   
|-- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
|   |                                                                                                                                                                                                                                                                                                                   
|2. | Based on my knowledge, this
  report does not contain any untrue statement of a material fact or omit to state
  a material fact necessary to make the statements made, in light of the
  circumstances under which such statements were made, not misleading with
  respect to the period covered by this report;
|   |                                                                                                                                                                                                                                                                                                                   
|3. | Based on my knowledge, the
  financial statements, and other financial information included in this
  report, fairly present in all material respects the financial condition,
  results of operations and cash flows of the registrant as of, and for, the
  periods presented in this report;                   
|   |                                                                                                                                                                                                                                                                                                                   
|4. | The registrants other
  certifying officer(s) and I are responsible for establishing and maintaining
  disclosure controls and procedures (as defined in Exchange Act Rules
  13a-15(e) and 15d-15(e)) for the registrant and have:                                                                              
|   |                                                                                                                                                                                                                                                                                                                   
|   | a)                                                                                                                                                                                                                                                                                                                
|   |                                                                                                                                                                                                                                                                                                                   
|   | b)                                                                                                                                                                                                                                                                                                                
|   |                                                                                                                                                                                                                                                                                                                   
|   | c)                                                                                                                                                                                                                                                                                                                
|   |                                                                                                                                                                                                                                                                                                                   
|   | d)                                                                                                                                                                                                                                                                                                                
|   |                                                                                                                                                                                                                                                                                                                   
|5. | The registrants other
  certifying officer(s) and I have disclosed, based on our most recent
  evaluation of internal control over financial reporting, to the registrants
  auditors and the audit committee of the registrants board of directors (or
  persons performing the equivalent functions):        
|   |                                                                                                                                                                                                                                                                                                                   
|   | a)                                                                                                                                                                                                                                                                                                                
|   |                                                                                                                                                                                                                                                                                                                   
|   | b)                                                                                                                                                                                                                                                                                                                

Date:  May 10, 2004

|/s/ William M. Clancy          | 
|------------------------------ | 
|                               | 
|William M. Clancy              | 
|Principal Accounting
  Officer | 
|                               | 

17

---

---