Comments on "A low-pass biquad derived filter realization"

In the above paper, Brodie (see ibid., vol.SC-11, p.552-5, 1976) presents a biquad low-pass filter which requires only two operational amplifiers. The use of current differencing amplifiers for reduced operational amplifier count implementation of the biquad filter has been around for some time. However, Brodie does not mention that the low-pass form is not the only filter that can be achieved. If one allows one additional resistor for biasing, a true bandpass output is available.