# What is the frequency response of a charge mode amplifier?

I'm having some difficulty understanding the frequency response of a charge mode amplifier, circuit shown in Figure 1 below.

                        Figure 1: Ideal charge mode amplifier circuit (1)


I believe I understand the principles behind an charge mode amplifier circuit, however I'm rather confused about the frequency response. Considering Figure 1 above, my understanding is that R1 and Cf will act as a low pass filter, where frequencies above a specific cutoff frequency (related to values of R1 and Cf) will be attenuated. However, having had a read through a Texas Instruments (TI) PDF (2) discussing this type of circuit, the frequency response doesn't appear to follow this rule (I was expecting a low pass filter response). The circuit and frequency response described by TI is shown in Figure 2 below.

            Figure 2: Practical charge mode amplifier and frequency response (2)


I'd really appreciate if someone could help me understand this.

# References

• Those are two different circuits. The first has one pole in its transfer function, the other 2 plus a pole at $\omega=0$. First: $i_1=-i_F => \frac{V_{in}}{R_i}=-V_o.j\omega C$ so $\frac{V_o}{V_{in}}=-\frac{1}{j \omega R_i C}$: A pole at $\omega=0$. – HarryH Jun 9 '18 at 18:56