How do you get the OP_HASH160 value from a bitcoin address? I'm trying to sign a coinbase transaction. I know I need to use 76 A9 14 (HASH160) 88 AC but I don't understand how to create the HASH160 (20 byte) from a bitcoin address.
Check the Wiki. I think what you are looking for is point 3:


  How to create Bitcoin Address
  
  0 - Having a private ECDSA key
  
  18E14A7B6A307F426A94F8114701E7C8E774E7F9A47E2C2035DB29A206321725
  
  1 - Take the corresponding public key generated with it (65 bytes, 1
  byte 0x04, 32 bytes corresponding to X coordinate, 32 bytes
  corresponding to Y coordinate)
  
  0450863AD64A87AE8A2FE83C1AF1A8403CB53F53E486D8511DAD8A04887E5B23522CD470243453A299FA9E77237716103ABC11A1DF38855ED6F2EE187E9C582BA6
  
  2 - Perform SHA-256 hashing on the public key
  
  600FFE422B4E00731A59557A5CCA46CC183944191006324A447BDB2D98D4B408
  
  3 - Perform RIPEMD-160 hashing on the result of SHA-256
  
  010966776006953D5567439E5E39F86A0D273BEE
  
  4 - Add version byte in front of RIPEMD-160 hash (0x00 for Main
  Network)
  
  00010966776006953D5567439E5E39F86A0D273BEE
  
  5 - Perform SHA-256 hash on the extended RIPEMD-160 result
  
  445C7A8007A93D8733188288BB320A8FE2DEBD2AE1B47F0F50BC10BAE845C094
  
  6 - Perform SHA-256 hash on the result of the previous SHA-256 hash
  
  D61967F63C7DD183914A4AE452C9F6AD5D462CE3D277798075B107615C1A8A30
  
  7 - Take the first 4 bytes of the second SHA-256 hash. This is the
  address checksum
  
  D61967F6
  
  8 - Add the 4 checksum bytes from point 7 at the end of extended
  RIPEMD-160 hash from point 4. This is the 25-byte binary Bitcoin
  Address.
  
  00010966776006953D5567439E5E39F86A0D273BEED61967F6
  
  9 - Convert the result from a byte string into a base58 string using
  Base58Check encoding. This is the most commonly used Bitcoin Address
  format
  
  16UwLL9Risc3QfPqBUvKofHmBQ7wMtjvM


You can check your calculations against my testing suite.