In ultra-high speed visible light communications (VLC) with light emitting diodes (LEDs) as the transmitter, analog pre-equalizers are often adopted to extend the modulation bandwidth. However, pre-equalizer may severely degrade the signal-to-noise-ratio (SNR) in the low frequency if we only focus on its bandwidth extending feature. And therefore, an important issue is that there exists a tradeoff between extending the system bandwidth and improving the SNR. In this paper, we first study the small signal characteristics of LEDs using the ABC parameters by taking into account of its internal quantum efficiency. And then, we propose an asymmetric bridged-T pre-equalizer considering an impedance matching network, based on which we study the bandwidth-SNR tradeoff problem via analytical derivations. We formulate a data rate maximization problem by considering the above tradeoff issue. Interestingly, different from common intuition, simulations results indicate that when the LED driving current and modulation bandwidth both reach maximal values, the achievable rate cannot reach the highest point. Specifically, using an OSRAM green LED, a maximum data rate of 1.15 Gbps can be achieved with a bias current of 378.63 mA and transmitter bandwidth of 163.31 MHz. The simulated data rate is 1.47 times higher than that of the literature using similar LED with 1/2 of the signal power attenuation. In the future, we will based on the optimized LED driving and equalization circuit to design PCB and test its impacts in real deployments.