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Unformatted text preview: Assignment Quiz 1 Assignment Quiz A The analysis of the high frequency response of a CS amplifier is based on assumption that the resistance of the signal source is large and thus its interaction with the i/p capacitance produces a dominant pole that determines the upper 3dB frequency . There are situations however , when the CS amplifier is fed with a very low resistance . Fig 1 shows the equivalent cct with an ideal voltage Source having = 0. By writing a node equation at the o/p, show that the transfer function is given as: At frequencies the s term in the numerator can be neglected. In such Case what is the upper 3dB frequency? Compute the value of & for the Case =0.5pF, =2pF, =4mA/V, and 2 in C H f sig R L gd L m gd L m sig O R C C s g C s R g V V ' ' ) ( 1 ) / ( 1 + + = ) ( gd m C g < < ϖ M A H f gd C L C m g ' L R Assignment Quiz C Draw a complete high frequency model of the following circuit. (including all the capacitors & resistors) Be sure to draw ‘pi’/’T’ model according to the configuration. Identify the two amplifier stages. 3 4 BJT Capacitance & Frequency Response 5 High Frequency Hybrid π Model • The BJT amplifiers we have examined so far are all low frequency amplifiers. • For large values of DC blocking capacitors and for frequencies of ten to hundred of kHz the simple small signal model that we have used will work well....
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 Spring '10
 mamamia
 Amplifier, Frequency, Electronics terms, Vsig Vπ

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