As Apple shares are plunging due to Steve Jobs' renewed health concerns, some Street analysts think it is a good buying opportunity to accumulate shares as Apple is expected to report upbeat numbers, when it reports its quarterly results today.

Wall Street expects Apple to earn $5.38 a share on revenue of $24.38 billion for the first quarter, according to analysts polled by Thomson Reuters.

We view likely weakness in the stock ahead of the 1QFY11 report to be a good buying opportunity given our belief that AAPL is likely to report strong momentum driven by supply-unconstrained iPad traction, global distribution expansion of the iPhone and new product cycles in the iPod and Macbook Air, analyst Rajesh Ghai at ThinkEquity wrote in a note to clients.

The analyst, who has a buy rating on Apple stock, said though the duration of Steve Jobs medical leave is unclear, it will not have any significant near-term impact on Apple's projected fortunes. Ghai also raised his price target on Apple stock to $390 from $375.

We highlight a busy product roadmap in 2011 which includes potential refreshes to the iPad, iPhone and the Macs and the expansion of the iPhone on to the Verizon network, as key reasons why AAPL will likely maintain momentum for the foreseeable future, Ghai said.

The analyst also expressed his belief in the managerial abilities of Tim Cook, who is managing day to day operations on Jobs' absence.

We also point out that COO Tom Cook is the key Executive behind what we view as AAPL's flawless operational execution and given his past record, we believe remains likely to ensure continued strong execution and maintenance of the company's culture of innovation, the analyst said.

Ghai, who now expects Apple to report first quarter earnings of $5.50 a share on revenue of $25.13 billion, raised his iPad estimate for the quarter to 7.5 million units from 6.5 million units and for fiscal 2011 to 30.5 million units from 26.5 million units.

At current levels, we believe shares are still cheap. On an ex-cash basis, at Friday's close, shares traded at less than 14 times our new FY11 EPS estimate, which appears to be an attractive entry point considering our expectation of over 40 percent growth for FY11, Ghai said.

Meanwhile, Yair Reiner - an analyst at Oppenheimer said: ..this worry stage (Jobs health concerns) will likely run out of fuel relatively quickly, because convincing evidence of how Jobs' presence or absence is impacting Apple's fundamentals won't present itself for years. Lacking evidence, investors will shortly go back to trading AAPL's stock based on measurable fundamental performance.

As we expect these to remain strong in 2011-12, we're buyers at current attractive valuation, said Reiner, who has an outperform rating and $395 price target on Apple stock.

Another analyst Jeffrey Fidacaro, who is with Susquehanna Financial, said he anticipates continued demand momentum for the iPhone and iPad product lines, including the recent launch of the iPhone at Verizon, as well as solid Mac sales. He also expects the upcoming refresh of the iPad at the end of March/April and the iPhone in July to be well-received.

Fidacaro, who has a positive rating on Apple stock, also wrote an interesting point: While we acknowledge that Steve Jobs is the visionary of Apple and is very influential in every aspect from product design to marketing, we note that during his previous leave in 2009 from January 14 to June 29, Apple's share rose 66%.

Shares of California-based Apple were down $15.15, or 4.3 percent, to trade at $333.33 on Nasdaq.