For a common emitter configuration, if $\mathrm{\alpha }$ and $\mathrm{\beta }$ have their usual meanings, the correct relationship between $\mathrm{\alpha }$ and $\mathrm{\beta }$ is:

• Correct answer
  A

  $\mathrm{\alpha }=\frac{\mathrm{\beta }}{1+\mathrm{\beta }}$
• B

  ${\alpha }^{}=\frac{{\mathrm{\beta }}^2}{1+{\mathrm{\beta }}^2}$
• C

  $\frac{1}{\mathrm{\alpha }}=\frac{1}{\mathrm{\beta }}-1$
• D

  $\mathrm{\alpha }=\frac{\mathrm{\beta }}{1-\mathrm{\beta }}$

Hence, the correct answer is option: 'A'.