A signal analyzing circuit is described, with at least a first channel, the first channel comprising a digitizer configured to digitize an input signal into a time-and-value-discrete signal; a switching unit coupled to the digitizer, the switching unit being adapted to receive the time-and-value-discrete signal and an acquisition memory coupled to the switching unit. The switching unit is adapted to selectively activate a decimator unit in a time-domain operation mode, the decimator unit decimating the time-and-vale-discrete signal to a decimated time-and-value-discrete signal or a digital down converter unit in a spectrum view operation mode, the digital down converter unit down-converting the time-and-value-discrete signal to a down-converted time-and-value-discrete signal. The aid acquisition memory is coupled to the decimator unit in the time-domain operation mode to store the decimated time-and-value-discrete signal, the acquisition memory being not coupled to the digital down converter unit in the time-domain operation mode. The acquisition memory is coupled to the digital down converter unit in the spectrum view operation mode to store the down-converted time-and-value-discrete signal, the acquisition memory being not coupled to the decimator unit in the spectrum view operation mode. In addition, an oscilloscope and a method for auto setting an oscilloscope are described.