- 
        Signature
      
- 
        /s/ Eva Wen, by power of attorney
      
      
- 
        Stock symbol
      
- 
        AMPH
      
      
- 
        Transactions as of
      
- 
        Feb 25, 2022
      
      
- 
        Transactions value $
      
- 
        -$304,577
      
      
- 
        Form type
      
- 
        4
      
      
- 
        Date filed
      
- 
        3/1/2022, 03:07 PM
      
 
     
   
 
  
    Transactions Table
  
  
    
      
        
          | Type | Sym | Class | Transaction | Value $ | Shares | Change % | * Price $ | Shares After | Date | Ownership | Footnotes | 
      
      
          
            | transaction | AMPH | Common Stock | Options Exercise | $76.5K | +7K | +9.14% | $10.93* | 83.6K | Feb 25, 2022 | Direct |  | 
          
            | transaction | AMPH | Common Stock | Sale | -$381K | -13.2K | -15.85% | $28.77 | 70.3K | Feb 25, 2022 | Direct | F1 | 
          
            | holding | AMPH | Common Stock |  |  |  |  |  | 99.7K | Feb 25, 2022 | See footnote | F2 | 
          
            | holding | AMPH | Common Stock |  |  |  |  |  | 5K | Feb 25, 2022 | See footnote | F3 | 
      
    
   
  
    Derivative Securities (e.g., puts, calls, warrants, options, convertible securities)
  
  
    
      
        
          | Type | Sym | Class | Transaction | Value $ | Shares | Change % | * Price $ | Shares After | Date | Underlying Class | Amount | Exercise Price | Ownership | Footnotes | 
      
      
          
            | transaction | AMPH | Employee Stock Option (right to buy) | Options Exercise | $0 | -7K | -100% | $0.00* | 0 | Feb 25, 2022 | Common Stock | 7K | $10.93 | Direct | F4 | 
      
    
   
  
    * An asterisk sign (*) next to the price indicates that the price is likely invalid.
  
  
    Explanation of Responses:
  
  
  
    Remarks:
  
  * If the form is filed by more than one reporting person, see Instruction 4(b)(v).