# Correct transfer function with 1st order IIR filter

What diffreneces it makes in magnitude and/or phase response when using

$$H(z) = \frac{b_0 + b_1z^{-1} + b_2z^{-2}}{a_0 + a_1z^{-1} + a_2z^{-2}}$$ by adding $b_2=0$, $a_2=0$

$$H(z) = \frac{b_0 + b_1z^{-1}}{a_0 + a_1z^{-1}}$$