palmeiras
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Good morning,
Please, I have a basic question about BJT operation:
Consider a device Q1 (BJT), with base and collector terminals connected together, with a bias current: I_bias. This device has BETA (common-emitter current gain) equal to X.
Now, consider a second device Q2, another BJT that also has the base and collector terminals connected together, with the same bias current I_bias. However, Q2 has an emitter area 8 times larger than device Q1. In other words, there are 8 devices Q1 connected in parallel.
What is beta of transistor Q2?
I know that BETA of bipolar transistor is defined by 1/(Dp/DN)*(NA/Nd)*(W*Lp) + 0.5*(W^2/Dn*taub).
As the effective width of the base terminal does not change, I supposed that the BETA does not change too. But I`m not sure. Could somebody help me?
Where:
Dp: hole diffusivity in the emitter,
Dn: electron diffusivity in the base,
Lp: hole diffusion length in the emitter,
ND: doping concentration of the emitter,
NA: doping concentration of the base,
W: effective width of the base,
Tau: minority-carrier lifetime,
Thank you very much,
Best Regards,
Palmeiras,
Please, I have a basic question about BJT operation:
Consider a device Q1 (BJT), with base and collector terminals connected together, with a bias current: I_bias. This device has BETA (common-emitter current gain) equal to X.
Now, consider a second device Q2, another BJT that also has the base and collector terminals connected together, with the same bias current I_bias. However, Q2 has an emitter area 8 times larger than device Q1. In other words, there are 8 devices Q1 connected in parallel.
What is beta of transistor Q2?
I know that BETA of bipolar transistor is defined by 1/(Dp/DN)*(NA/Nd)*(W*Lp) + 0.5*(W^2/Dn*taub).
As the effective width of the base terminal does not change, I supposed that the BETA does not change too. But I`m not sure. Could somebody help me?
Where:
Dp: hole diffusivity in the emitter,
Dn: electron diffusivity in the base,
Lp: hole diffusion length in the emitter,
ND: doping concentration of the emitter,
NA: doping concentration of the base,
W: effective width of the base,
Tau: minority-carrier lifetime,
Thank you very much,
Best Regards,
Palmeiras,