# Finding component values of bandpass filter with load

filter

I have to find the components of a bandpass filter given only the two corner frequencies. The only components are \$C_1\$ and \$R_1\$ for the high pass, and \$R_2\$, \$C_2\$, and Load resistance (\$5\$M\$\Omega\$) on the low pass.

I set \$R_1\$ to \$10\$k\$\Omega\$ and got \$C_1 = 53.05\$nF when corner frequency for high pass is \$300\$Hz using \$C=1/2\pi fR_1\$.

However, for the low pass… I can't figure it out. I combined \$C_2\$ and the load into equivalent impedance \$Z\$ (they are in parallel), then plugged \$Z\$ into the transfer equation for a low pass filter where ever a \$C\$ would have normally appeared, and get \$C_2 = 1.588\$nF while \$R_2 = 10\$k\$\Omega\$ (setting transfer of low pass filter equal to \$1/\sqrt{2}\$). Also corner frequency of low pass filter is 10kHz. But the graph of the output voltage looks like a high pass filter only, and is in the micro volts and the -3db frequencies are nowhere even close… I don't get what is going wrong with the low pass filter

So was wondering if anyone can show me how to calculate the \$R\$ and \$C\$ values of the low pass filter part of a bandpass filter when it is connected to a load?

It is quite a basic bandpass filter, but imagine a 5Mohm load where Vout is.