1AM is a code name not a model, it is a common NPN triode, model number MMBT3904L. 2)2A is MMBT3906, is a general purpose transistor, it is characterized by continuous voltage adjustable, low dynamic output resistance, flat temperature characteristics, low output voltage noise. Second, introduction: There are three operating states of the transistor, amplification, saturation, cut-off. Among them, the amplification state is the most complex, mainly used in the field of small signal amplification, commonly used triode amplifier circuit forms are: common emitter amplifier circuit, common collector amplifier circuit, common base amplifier circuit three kinds, of which common set circuit for current amplification (power amplification), common base circuit for high-frequency amplification, common radio circuit for low-frequency amplification. Triode amplifier circuit contains static parameters and dynamic parameters of two categories, static parameters, also known as static operating point, is to ensure the normal operation of the basis of the transistor, meaning that when the input condition is zero, the transistor base current Ib, collector current Ic,be between the voltage Ubc, tube voltage drop Uceq. When there is an input signal, the input resistance Ri, output resistance Ro, voltage gain Au and other parameters presented by the transistor are called dynamic parameters.
In addition, there is a class of parameters known as the frequency characteristic parameters of the amplifier circuit, mainly including the low frequency cut-off frequency of the amplifier circuit, the high frequency cut-off frequency, the pass band, the gain flatness, the amplitude (degree) frequency (rate) characteristic curve.
1AM is a NPN chip triode, model MMBT3904LT1, which can be replaced by MMBTA05LT1. MMBT3904LT1 Main technical parameters: Vcbo=60VIcm=200mAPcm =200mWfT=300MhzMMBTA05LT1 Main technical parameters: Vcbo=60VIcm=500mAPcm =300mWfT=100Mhz2 kinds of audion are SOT-23 package. 2A is MMBT3906, is a general purpose transistor, it is characterized by continuous voltage adjustable, low dynamic output resistance, flat temperature characteristics, low output voltage noise