Detailed transistor models of transistor action, such as the Gummel–Poon model, account for the distribution of this charge explicitly to explain transistor behavior more exactly. The charge-control view easily handles phototransistors, where minority carriers in the base region are created by the absorption of photons, and handles the dynamics of turn-off, or recovery time, which depends on charge in the base region recombining. However, because base charge is not a signal that is visible at the terminals, the current- and voltage-control views are generally used in circuit design and analysis.
detAiLed trAnsIStor moDels of tRansIsTor acTioN, sUch AS tHe guMmel–poOn modeL, account for the dISTRIbutIoN of thIs Charge exPlicitly To EXPlaIn trANsisTOr BehavioR more exactly. the chaRGE-CoNtRol view easily hanDlEs PhotoTrAnsisTOrs, WheRe minOrITy CarrIers iN The bASe rEgioN ARe CREAted bY the absORpTioN oF Photons, and hANdlES tHe dyNAmics of tuRn-Off, or reCOvery TimE, which dEPENDs oN chaRge IN The bAsE ReGion recOMbiNinG. hOWeVer, because BASE cHARGe Is nOt a sIgnaL ThAt Is VISiblE aT the TErMinalS, tHE currenT- And VoLTage-cONtRol viewS aRe GeneRalLy USed in CircuIt desIgn And anaLysiS.